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Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Tag: Sherline

Sherline CNC mill

  • Logitech Gamepad as EMC2 Pendant: Eagle Schematics for the Joggy Thing!

    Another pass at my Logitech Dual-Action Gamepad used as an EMC2 control pendant, but this time using an Eagle ULP (User Language Program) that converts a schematic into EMC2 HAL code.

    I tweaked Martin Schöneck’s original ULP a bit, added (some of the) new devices found in EMC2.4, added the corresponding Eagle symbols & devices to the library, then drew up a schematic based on my hand-hewn HAL code with some improvements. Ran the script and shazam the HAL code worked just fine (after a bit of debugging the infrastructure, of course).

    The new ULP and library are not quite ready for prime time, but this is a stick in the ground to mark some progress. You can certainly use the HAL code directly, without fiddling around in the schematic: stuff the whole program (at the end of the post) in your existing (but likely empty) custom_postgui.hal file.

    The schematic is, of course, much fluffier than the corresponding code, particularly because I chopped it into five easily printed pages. Here’s the Big Picture overview of what’s going on in each page; click the pix for bigger images.

    The servo thread interface device in the lower left provides the halui timing. The big block in the upper left has all the Logitech gamepad buttons, including the four big ones used for Z and A axis jogging. I changed the two left-rear buttons to activate the Abort signal rather than Estop, not that I use them all that much anyway.

    The two joystick knobs have pushbuttons, which I combine and use to toggle a flipflop that will select the jogging speed: fast or crawl.

    I also cut the jog deadband from 0.2 to 0.1, which makes the joysticks much more responsive.

    Logitech Gamepad HAL Schematic - Page 1
    Logitech Gamepad HAL Schematic – Page 1

    The big block on the left has all the gamepad’s analog axes. The HAT0X and HAT0Y axes correspond to the top-hat pushbuttons; they’re not really analog at all, although they take on -1.0 / 0.0 / + 1.0 floating point values. The window comparators determine which joystick axes are active, which comes in handy later on.

    Logitech Gamepad HAL Schematic - Page 2
    Logitech Gamepad HAL Schematic – Page 2

    The HAL jogging control has a single input that sets the default speed, but the proper value is vastly different depending on whether you’re jogging with linear or angular motion. This page picks out which ini file MAX_VELOCITY value to use, converts from units/sec to units/min, then does Cool Thing #1: scales the speed so that the fast/crawl speeds work out nicely.

    I use the buttons to jog rapidly from here to there, then creep up on the alignment point using the joysticks. Pressing the joysticks downward switches from Fast to Crawl speeds, which provides sort of a gearshift that’s useful for coarse / fine adjustments.

    The buttons run at two speeds:

    • Fast: the maximum speed for the axis
    • Crawl: 10% of that value

    The joysticks have a lower top speed:

    • Fast: half the maximum speed of the axis
    • Crawl: 10% of that value

    All those values go into the mux4 block and thence to the HAL jog speed control.

    Logitech Gamepad HAL Schematic - Page 3
    Logitech Gamepad HAL Schematic – Page 3

    This page does Cool Thing #2: prioritize the joystick axes and lock out the one that started moving last. The general idea is that it’s painfully easy to move the joysticks diagonally, which is great for gaming and terrible for milling machine control. A pair of flipflops for each joystick remember which axis started moving first.

    If you want to move diagonally, just press the buttons; they’re not locked out, so you can do what you want.

    Logitech Gamepad HAL Schematic - Page 4
    Logitech Gamepad HAL Schematic – Page 4

    The motion comes together on the last page, where scale blocks flip the direction of the Y and Z joystick axes so positive motion is upward. The multiplexers allow only the active axis of each joystick to reach the HAL analog jog inputs; you can vary the speed of that axis up to the maximum as you’d expect. The buttons drive the digital inputs that jog at that maximum speed; the Y and Z button directions get sorted out appropriately.

    Logitech Gamepad HAL Schematic - Page 5
    Logitech Gamepad HAL Schematic – Page 5

    Those five pages boil down into the following code, which I manually insert into my custom_postgui.hal file, along with the tool length probe pin definition.

    # HAL config file automatically generated by Eagle-CAD hal-write.ulp
    # (C) Martin Schoeneck.de 2008
    # Mods Ed Nisley 2010
    
    # Path: [/mnt/bulkdata/Project Files/eagle/projects/EMC2 HAL Configuration/]
    # ProjectName: [Logitech Gamepad]
    # File name: [/mnt/bulkdata/Project Files/eagle/projects/EMC2 HAL Configuration/Logitech Gamepad.hal]
    
    ####################################################
    # Load realtime and userspace modules
    loadrt constant	count=14
    loadrt and2	count=9
    loadrt flipflop	count=4
    loadrt mux2	count=5
    loadrt mux4	count=1
    loadrt not	count=8
    loadrt or2	count=9
    loadrt scale	count=7
    loadrt toggle	count=1
    loadrt wcomp	count=6
    
    ####################################################
    # Hook functions into threads
    addf toggle.0	servo-thread
    addf wcomp.1	servo-thread
    addf wcomp.2	servo-thread
    addf wcomp.3	servo-thread
    addf and2.0	servo-thread
    addf and2.4	servo-thread
    addf and2.3	servo-thread
    addf and2.2	servo-thread
    addf and2.1	servo-thread
    addf constant.6	servo-thread
    addf constant.5	servo-thread
    addf constant.4	servo-thread
    addf constant.3	servo-thread
    addf constant.2	servo-thread
    addf constant.1	servo-thread
    addf constant.0	servo-thread
    addf constant.7	servo-thread
    addf constant.8	servo-thread
    addf scale.1	servo-thread
    addf scale.2	servo-thread
    addf scale.3	servo-thread
    addf mux4.0	servo-thread
    addf mux2.0	servo-thread
    addf scale.4	servo-thread
    addf scale.0	servo-thread
    addf wcomp.5	servo-thread
    addf wcomp.4	servo-thread
    addf wcomp.0	servo-thread
    addf flipflop.1	servo-thread
    addf flipflop.0	servo-thread
    addf and2.5	servo-thread
    addf and2.6	servo-thread
    addf and2.7	servo-thread
    addf and2.8	servo-thread
    addf flipflop.2	servo-thread
    addf flipflop.3	servo-thread
    addf or2.4	servo-thread
    addf or2.8	servo-thread
    addf or2.7	servo-thread
    addf or2.6	servo-thread
    addf or2.5	servo-thread
    addf or2.3	servo-thread
    addf or2.2	servo-thread
    addf or2.1	servo-thread
    addf or2.0	servo-thread
    addf not.1	servo-thread
    addf not.2	servo-thread
    addf not.3	servo-thread
    addf not.4	servo-thread
    addf not.5	servo-thread
    addf not.6	servo-thread
    addf not.7	servo-thread
    addf not.0	servo-thread
    addf constant.9	servo-thread
    addf mux2.1	servo-thread
    addf mux2.2	servo-thread
    addf mux2.3	servo-thread
    addf mux2.4	servo-thread
    addf constant.10	servo-thread
    addf constant.11	servo-thread
    addf scale.5	servo-thread
    addf scale.6	servo-thread
    addf constant.12	servo-thread
    addf constant.13	servo-thread
    
    ####################################################
    # Set parameters
    
    ####################################################
    # Set constants
    setp constant.0.value	+0.02
    setp constant.1.value	-0.02
    setp constant.2.value	60
    setp constant.3.value	1.00
    setp constant.4.value	0.10
    setp constant.5.value	0.50
    setp constant.6.value	0.10
    setp constant.7.value	+0.5
    setp constant.8.value	-0.5
    setp constant.9.value	0.0
    setp constant.10.value	[TRAJ]MAX_LINEAR_VELOCITY
    setp constant.11.value	[TRAJ]MAX_ANGULAR_VELOCITY
    setp constant.12.value	-1.0
    setp constant.13.value	0.1
    
    ####################################################
    # Connect Modules with nets
    net a-button-minus input.0.btn-trigger or2.2.in0 halui.jog.3.minus
    net a-button-plus input.0.btn-thumb2 or2.2.in1 halui.jog.3.plus
    net a-buttons-active or2.2.out or2.3.in0 or2.4.in1
    net a-disable not.7.out and2.5.in1
    net a-enable flipflop.3.out not.7.in mux2.4.sel
    net a-jog wcomp.2.in input.0.abs-z-position mux2.4.in1
    net a-knob-active not.2.out or2.4.in0 and2.7.in1
    net a-knob-inactive wcomp.2.out not.2.in and2.6.in1
    net a-select and2.8.in0 and2.7.out
    net a-set flipflop.3.set and2.8.out
    net angular_motion or2.4.out mux2.0.sel
    net any-buttons-active mux4.0.sel0 or2.8.out
    net az-buttons-active or2.3.out or2.8.in1
    net az-reset flipflop.2.reset and2.6.out flipflop.3.reset
    net button-crawl scale.4.out mux4.0.in3
    net button-fast scale.2.out mux4.0.in1 scale.4.in
    net jog-crawl toggle.0.out mux4.0.sel1
    net jog-speed halui.jog-speed mux4.0.out
    net knob-crawl mux4.0.in2 scale.3.out
    net knob-fast mux4.0.in0 scale.1.out scale.3.in
    net n_1 constant.10.out mux2.0.in0
    net n_2 and2.0.in0 input.0.btn-top2
    net n_3 and2.0.in1 input.0.btn-base
    net n_4 and2.0.out halui.abort
    net n_5 halui.mode.manual input.0.btn-base3
    net n_6 wcomp.0.max wcomp.1.max wcomp.2.max wcomp.3.max constant.0.out
    net n_7 halui.program.resume input.0.btn-base4
    net n_8 wcomp.0.min wcomp.1.min wcomp.2.min wcomp.3.min constant.1.out
    net n_9 mux2.0.in1 constant.11.out
    net n_10 constant.12.out scale.5.gain scale.6.gain
    net n_11 input.0.btn-base5 or2.0.in0
    net n_12 input.0.btn-base6 or2.0.in1
    net n_13 constant.9.out mux2.1.in0 mux2.2.in0 mux2.3.in0 mux2.4.in0
    net n_14 mux2.1.out halui.jog.0.analog
    net n_15 toggle.0.in or2.0.out
    net n_16 constant.2.out scale.0.gain
    net n_17 constant.5.out scale.1.gain
    net n_18 constant.3.out scale.2.gain
    net n_19 constant.4.out scale.3.gain
    net n_20 scale.4.gain constant.6.out
    net n_21 halui.jog.1.analog mux2.2.out
    net n_22 mux2.2.in1 scale.5.out
    net n_23 scale.6.out mux2.3.in1
    net n_24 constant.13.out halui.jog-deadband
    net n_25 wcomp.4.max constant.7.out wcomp.5.max
    net n_26 constant.8.out wcomp.4.min wcomp.5.min
    net n_27 mux2.3.out halui.jog.2.analog
    net n_28 halui.jog.3.analog mux2.4.out
    net vel-per-minute scale.0.out scale.1.in scale.2.in
    net vel-per-second mux2.0.out scale.0.in
    net x-buttons-active or2.7.in0 or2.5.out
    net x-disable not.4.out and2.4.in1
    net x-enable not.4.in flipflop.0.out mux2.1.sel
    net x-hat-jog wcomp.4.in input.0.abs-hat0x-position
    net x-hat-minus wcomp.4.under or2.5.in1 halui.jog.0.minus
    net x-hat-plus or2.5.in0 wcomp.4.over halui.jog.0.plus
    net x-jog wcomp.0.in input.0.abs-x-position mux2.1.in1
    net x-knob-active not.0.out and2.1.in0
    net x-knob-inactive wcomp.0.out not.0.in and2.2.in0 and2.3.in0
    net x-set and2.1.out flipflop.0.set
    net xy-buttons-active or2.7.out or2.8.in0
    net xy-reset flipflop.0.reset and2.2.out flipflop.1.reset
    net y-buttons-active or2.6.out or2.7.in1
    net y-disable not.5.out and2.1.in1
    net y-enable flipflop.1.out not.5.in mux2.2.sel
    net y-hat-jog input.0.abs-hat0y-position wcomp.5.in
    net y-hat-minus wcomp.5.under or2.6.in1 halui.jog.1.plus
    net y-hat-plus or2.6.in0 wcomp.5.over halui.jog.1.minus
    net y-jog wcomp.1.in input.0.abs-y-position scale.5.in
    net y-knob-active not.1.out and2.3.in1
    net y-knob-inactive not.1.in wcomp.1.out and2.2.in1
    net y-select and2.4.in0 and2.3.out
    net y-set flipflop.1.set and2.4.out
    net z-button-minus input.0.btn-thumb or2.1.in0 halui.jog.2.minus
    net z-button-plus input.0.btn-top or2.1.in1 halui.jog.2.plus
    net z-buttons-active or2.1.out or2.3.in1
    net z-disable not.6.out and2.8.in1
    net z-enable not.6.in flipflop.2.out mux2.3.sel
    net z-jog wcomp.3.in input.0.abs-rz-position scale.6.in
    net z-knob-active not.3.out and2.5.in0
    net z-knob-inactive not.3.in wcomp.3.out and2.7.in0 and2.6.in0
    net z-set and2.5.out flipflop.2.set
    

    The ULP script that eats the schematic and poots out the HAL code:

    /******************************************************************************
     * HAL-Configurator
     *
     * Author: Martin Schoeneck 2008
     * Additional gates & tweaks: Ed Nisley KE4ZNU 2010
     *****************************************************************************/
    #usage "<h1>HAL-Configurator</h1>Start from a Schematic where symbols from hal-config.lbr are used!";
    
    string output_path =    "./";
    string dev_loadrt =     "LOADRT";
    string dev_loadusr =    "LOADUSR";
    string dev_thread =     "THREAD";
    string dev_parameter =  "PARAMETER";
    
    string dev_names[] = {
    "CONSTANT",								// must be first entry to make set_constants() work
    "ABS",				// 2.4
    "AND2",
    "BLEND",			// 2.4
    "CHARGE-PUMP",		// 2.4
    "COMP",
    "CONV_S32_FLOAT",	// 2.4
    "DDT",				// 2.4
    "DEADZONE",			// 2.4
    "DEBOUNCE",			// 2.4
    "EDGE",
    "ENCODER",			// 2.4
    "ENCODER-RATIO",	// 2.4
    "ESTOP-LATCH",
    "FLIPFLOP",
    "FREQGEN",			// 2.4
    "LOWPASS",
    "MULT2",			// 2.4
    "MUX2",
    "MUX4",				// 2.4
    "MUX8",				// 2.4
    "NEAR",				// 2.4
    "NOT",
    "ONESHOT",
    "OR2",
    "SAMPLER",			// 2.4
    "SCALE",			// 2.4
    "SELECT8",			// 2.4
    "SUM2",
    "TIMEDELAY",		// 2.4
    "TOGGLE",			// 2.4
    "WCOMP",			// 2.4
    "XOR2",				// 2.4
    ""					// end flag
    };
    
    string init = "# HAL config file automatically generated by Eagle-CAD hal-write.ulp\n# (C) Martin Schoeneck.de 2008\n# Mods Ed Nisley 2010\n";
    
    /*******************************************************************************
     * Global Stuff
     ******************************************************************************/
    
    string FileName;
    string ProjectPath;
    string ProjectName;
    
    void Info(string Message) {
    	dlgMessageBox(";<b>Info</b><p>\n" + Message);
    }
    
    void Warn(string Message) {
    	dlgMessageBox("!<b>Warning</b><p>\n" + Message + "<p>see usage");
    }
    
    void Error(string Message) {
    	dlgMessageBox(":<hr><b>Error</b><p>\n" + Message + "<p>see usage");
    	exit(1);
    }
    
    string replace(string str, char a, char b) {
    	// in string str replace a with b
    	int pos = -1;
    	do {
    		// find that character
    		pos = strchr(str, a);
    		// replace if found
    		if(pos >= 0) {
    			str[pos] = b;
    		}
    	} while(pos >= 0);
    
    	return str;
    }
    
    // the part name contains an index and is written in capital letters
    string get_module_name(UL_PART P) {
    	// check module name, syntax: INDEX:NAME
    	string mod_name = strlwr(P.name);
    	// split string at the : if exists
    	string a[];
    	int c = strsplit(a, mod_name, ':');
    	mod_name = a[c-1];
    	// if name starts with '[' we need uppercase letters
    	if(mod_name[0] == '[') {
    		mod_name = strupr(mod_name);
    	}
    
    	return mod_name;
    }
    
    string comment(string mess) {
    	string str = "\n\n####################################################\n";
    	if(mess != "") {
    		str += "# " + mess + "\n";
    	}
    
    	return str;
    }
    
    // if this is a device for loading a module, load it (usr/rt)
    string load_module(UL_PART P) {
    	string str = "";
    
    	// it's a module if the device's name starts with LOADRT/LOADUSR
    	if((strstr(P.device.name, dev_loadrt) == 0) ||
    	   (strstr(P.device.name, dev_loadusr) == 0)) {
    
    		// now add the string to our script
    		str += P.value + "\n";
    	}
    
    	return str;
    }
    
    // count used digital gates (and, or, etc) and load module if neccessary
    string load_blocks() {
    	string str = "";
    
    	int index;
    
    	int dev_counters[];
    	string dname[];
    
    	// count the gates that are used
    	schematic(S) { S.parts(P) {
    		strsplit(dname,P.device.name,'.');		// extract first part of name
    		if ("" != lookup(dev_names,dname[0],0)) {
    			for (index = 0;  (dname[0] != dev_names[index]) ; index++) {
    				continue;
    			}
    			dev_counters[index]++;
    		}
    	} }
    
    // force lowercase module names...
    
    	for (index = 0; ("" != dev_names[index]) ; index++) {
    		if (dev_counters[index]) {
    			sprintf(str,"%sloadrt %s\tcount=%d\n",str,strlwr(dev_names[index]),dev_counters[index]);
    		}
    	}
    
    	return str;
    }
    
    string hook_function(UL_NET N) {
    	string str = "";
    
    	// is this net connected to a thread (work as functions here)?
    	int    noclkpins       = 0;
    	string thread_name     = "";  // this net should be connected to a thread
    	string thread_position = "";
    	N.pinrefs(PR) {
    		// this net is connected to a clk-pin
    		if(PR.pin.function == PIN_FUNCTION_FLAG_CLK) {
    			// check the part: is it a thread-device?
    			if(strstr(PR.part.device.name, dev_thread) == 0) {
    				// we need the name of the thread
    				thread_name = strlwr(PR.part.name);
    				// and we need the position (position _ is ignored)
    				thread_position = strlwr(PR.pin.name);
    				thread_position = replace(thread_position, '_', ' ');
    			}
    		} else {
    			// no clk-pin, this is no function-net
    			noclkpins++;
    			break;
    		}
    	}
    
    	// found a thread?
    	if(noclkpins == 0 && thread_name != "") {
    		// all the other pins are interesting now
    		N.pinrefs(PR) {
    			// this pin does not belong to the thread
    			if(strstr(PR.part.device.name, dev_thread) != 0) {
    				// name of the pin is name of the function
    				//string function_name = strlwr(PR.pin.name);
    				string function_name = strlwr(PR.instance.gate.name);
    				// if functionname starts with a '.', it will be appended to the modulename
    				if(function_name[0] == '.') {
    					// if the name is only a point, it will be ignored
    					if(strlen(function_name) == 1) {
    						function_name = "";
    					}
    					function_name = get_module_name(PR.part) + function_name;
    				}
    				str += "addf " + function_name + "\t" + thread_name + "\t" + thread_position + "\n";
    			}
    		}
    	}
    
    	return str;
    }
    
    string set_parameter(UL_NET N) {
    	string str = "";
    
    	// is this net connected to a parameter-device?
    	int    nodotpins       = 0;
    	string parameter_value = "";
    	N.pinrefs(PR) {
    		// this net is connected to a dot-pin
    		if(PR.pin.function == PIN_FUNCTION_FLAG_DOT) {
    			// check the part: is it a parameter-device?
    //			str += "** dev name [" + PR.part.device.name + "] [" + dev_parameter + "]\n";
    			if(strstr(PR.part.device.name, dev_parameter) == 0) {
    				// we need the value of that parameter
    				parameter_value = PR.part.value;
    //				str += "**  value [" + PR.part.value +"]\n";
    			}
    		} else {
    			// no clk-pin, this is no function-net
    			nodotpins++;
    			break;
    		}
    	}
    
    	// found a parameter?
    	if(nodotpins == 0 && parameter_value != "") {
    		// all the other pins are interesting now
    		N.pinrefs(PR) {
    //			str += "** dev name [" + PR.part.device.name + "] [" + dev_parameter + "]\n";
    			// this pin does not belong to the parameter-device
    			if(strstr(PR.part.device.name, dev_parameter) != 0) {
    				// name of the pin is name of the function
    				//string parameter_name = strlwr(PR.pin.name);
    				string parameter_name = strlwr(PR.instance.gate.name);
    				// if functionname starts with a '.', it will be appended to the modulename
    //				str += "** param (gate) name [" + parameter_name + "]\n";
    				if(parameter_name[0] == '.') {
    					// if the name is only a point, it will be ignored
    					if(strlen(parameter_name) == 1) {
    						parameter_name = "";
    					}
    					parameter_name = get_module_name(PR.part) + parameter_name;
    //					str += "** param (part) name [" + parameter_name + "]\n";
    				}
    				str += "setp " + parameter_name + "\t" + parameter_value + "\n";
    			}
    		}
    	}
    
    	return str;
    }
    
    // if this is a 'constant'-device, set its value
    // NOTE: this is hardcoded to use the first entry in the dev_names[] array!
    string set_constants(UL_PART P) {
    	string str = "";
    
    	// 'constant'-device?
    	if(strstr(P.device.name, dev_names[0]) == 0) {
    		str += "setp " + get_module_name(P) + ".value\t" + P.value + "\n";
    	}
    
    	return str;
    }
    
    string connect_net(UL_NET N) {
    	string str = "";
    
    	// find all neccessary net-members
    	string pins = "";
    	N.pinrefs(P) {
    		// only non-functional pins are connected
    		if(P.pin.function == PIN_FUNCTION_FLAG_NONE) {
    			string pin_name =  strlwr(P.pin.name);
    			string part_name = strlwr(P.part.name);
    			pin_name =  replace(pin_name,  '$', '_');
    			part_name = replace(part_name, '$', '_');
    			pins += part_name + "." + pin_name + " ";
    		}
    	}
    
    	if(pins != "") {
    		string net_name = strlwr(N.name);
    		net_name = replace(net_name, '$', '_');
    		str += "net " + net_name + " " + pins + "\n";
    	}
    
    	return str;
    }
    
    /*******************************************************************************
     * Main program.
     ******************************************************************************/
    // is the schematic editor running?
    if (!schematic) {
    	Error("No Schematic!<br>This program will only work in the schematic editor.");
    }
    
    schematic(S) {
    	ProjectPath = filedir(S.name);
    	ProjectName = filesetext(filename(S.name), "");
    }
    
    // build configuration
    string cs = init + "\n\n";
    
    FileName = ProjectPath + ProjectName + ".hal";
    
    cs += "# Path: [" + ProjectPath + "]\n";
    cs += "# ProjectName: [" + ProjectName + "]\n";
    //cs += "# File name: [" + FileName + "]\n\n";
    
    // ask for a filename: where should we write the configuration?
    
    FileName = dlgFileSave("Save Configuration", FileName, "*.hal");
    
    if(!FileName) {
    	exit(0);
    }
    
    cs += "# File name: [" + FileName + "]\n\n";
    
    schematic(S) {
    	// load modules
    	cs += comment("Load realtime and userspace modules");
    	S.parts(P) {
    		cs += load_module(P);
    	}
    
    	// load blocks
    	cs += load_blocks();
    
    	// add functions
    	cs += comment("Hook functions into threads");
    	S.nets(N) {
    		cs += hook_function(N);
    	}
    
    	// set parameters
    	cs += comment("Set parameters");
    	S.nets(N) {
    		cs += set_parameter(N);
    	}
    
    	// set constant values
    	cs += comment("Set constants");
    	S.parts(P) {
    		cs += set_constants(P);
    	}
    
    	// build nets and connect them
    	cs += comment("Connect Modules with nets");
    	S.nets(N) {
    		cs += connect_net(N);
    	}
    }
    
    // open/overwrite the target file to save the configuration
    output(FileName, "wt") {
    	printf(cs);
    }
    

    Most of that script is Martin’s work; I just cleaned it up. You can download it by hovering over the code to make the little toolbar pop up near the upper-right corner of the text, then:

    • click a little button to copy it to the clipboard or
    • click another little button to view the source, then save that file

    You’ll also need the Eagle library that goes along with the script, but WordPress doesn’t like .lbr files. Here’s the hal-config-2.4.lbr file with a totally bogus odt extension. Download it, rename it to remove the .odt extension, and it’s all good.

    There is basically no documentation for any of this. I figured out what to do by looking at the source and Martin’s sample schematic, but now you have two sample schematics: the situation is definitely improving!

  • Water Bottles: Adding a Vent Plug

    Those water bottles turned out to have an unexpected feature: the vent hole dribbles when they’re laid sideways. I think it’s an unfortunate side effect of a product cheapnification: the spout is slightly concave on the side that could seal the vent, so surface tension sucks water out of the hole.

    The hole is to the right of the spout, in the center of the transverse ridge. Looks like a little black dot here; clicky for a somewhat bigger image.

     

    Water bottle cap showing vent hole
    Water bottle cap showing vent hole

     

    The solution is to put a silicone plug at the Spot Marked X on the spout, which I marked by running a small punch through the vent hole and scarring the spout. You might be able to see the tiny mark on the spout if you look closely.

    The spout comes out of the cap with a firm pull, but the sockets in the cap are obviously not intended to take much of that abuse. It’s not clear to me that the designers of these things ever take cleaning into consideration; past experience says you must completely dismantle fluid-facing components to get the crud out.

    Anyway.

    Chuck the spout up in the Sherline mill, align over the spot, and mill a 1/8 inch diameter flat-bottom hole 0.100 inch deep. The spout has a large finger-friendly flange directly underneath the Spot Marked X, so this setup isn’t quite as precarious as it looks.

     

    Milling socket for vent plug
    Milling socket for vent plug

     

    Dab in a little silicone caulk, leave a mostly flat surface standing just higher than the spout’s concavity, and we’ll see how well it works.

     

    Vent plug
    Vent plug

     

    The little nub just to the left of the new plug (on the ball-shaped part of the spout) engages the edge of the socket in the cap to sorta-kinda hold the spout closed. Doesn’t really accomplish much, but it’s a nice thought.

  • Screwdriver Bit Ball Repair: Rubberdraulics!

    Went to use a small multi-bit screwdriver and the bit fell right out: evidently, the ball wasn’t swaged tightly enough; it and the spring went walkabout. Given that I don’t know when or where that might have happened, there’s no chance I’ll ever see those parts again.

    Screwdriver bit with missing ball
    Screwdriver bit with missing ball

    But I do have some 2 mm steel bearings that aren’t grossly oversized, so all hope is not lost. Alas, I have no idea what sort of spring to put in there, other than that I don’t have one of those.

    Drilled hole with ball
    Drilled hole with ball

    This looks like an application for rubberdraulics: use compliant silicone snot rubber as a spring. Lautard described a use with a lock ring and an external screw to apply pressure, but here it’ll work fine to allow a small motion for a tiny ball.

    Drill out the recess barely larger than the ball: the slight clearance allows the cured rubber to squish out around the ball. I clamped it in the Sherline vise and jogged into position by eyeball, then poked a hole with G83 down 1.5 mm. The original recess was a bit over 2 mm deep, so there’s plenty of room for the silicone in the bottom.

    Then mush some silicone into the hole, install the ball, push it down until it stands barely proud of the surface, scrape off the excess rubber, and let it cure overnight.

    New ball in place
    New ball in place

    There, now, that wasn’t so bad, was it?

  • Broken Tap Removal: The CNC Way

    Having successfully drilled and tapped eight 4-40 holes for the MOSFETs and two 8-32 holes for the heatsink clamps, I needed four more holes for the 6-32 standoffs that will mount the heat spreader to the base. As is always the case, the tap broke in the next-to-last hole…

    Broken tap
    Broken tap

    This is a three-flute tap, the break is recessed below the surface, and it looks like it’s cracked along one of the flutes. Bleh! I don’t have any tap extractors, mostly because I don’t do that much tapping, and I doubt the extractors work all that well on tiny taps.

    I tried something I’d never done before: slit the top of the tap with an abrasive wheel and unscrew it. That didn’t work, of course, but it’s a useful trick to keep in mind. I think the tap was cracked lengthwise and, in any event, a three-flute tap doesn’t have the proper symmetry for a slot. Better luck with larger four-flute taps.

    Slotted tap
    Slotted tap

    So I must dig the mumble thing out…

    Starting the moat
    Starting the moat

    The overall plan:

    • Clamp the heat spreader to the Sherline tooling plate
    • Helix-mill a trench around the tap
    • Grab the stub with Vise-Grips
    • Unscrew it
    • Repair the damage

    The clearance hole for a 6-32 screw is 0.1405 inch and that’s a 3/16-inch end mill: 70 + 93 = 163 mil radius, call it 0.170 inch. You really don’t want to kiss the tap flutes with the end mill, so you could make that the ID a bit larger.

    Manual CNC, feeding commands into Axis and using the history list to chew downward 20 mils on each pass. With the origin in the middle of the broken tap and the cutter starting at (-0.170,0), the code looks like:

    G2 I+0.170 Z=-0.020
    G2 I+0.170 Z=-0.040
    ... and so on ...
    

    About 3000 rpm and 2 inches per minute feed; the feed was too slow, because the aluminum chips were much too fine. I actually used cutting lube for this job: the heat spreader got nice and warm.

    Coolant
    Coolant

    I stopped at Z=-0.100 and made a final pass around the bottom of the hole to clean out the ramp. Then, try unscrewing the tap…

    Tap stub - first attempt
    Tap stub – first attempt

    Of course, the stub broke off more or less flush with the bottom of the hole, so I continued milling downward to Z=-0.260, a bit more than halfway through the plate. This time, the needle-nose Vise-Grips got a good grip on an uncracked section and the remains twisted out with very little effort.

    Grabbing the stub
    Grabbing the stub

    Although the central pillar is outside the tap’s OD, leaving a solid aluminum shell, there’s not much meat to it. The shell broke off with the first twist and came out with the tap.

    Those are not, by the way, gold-plated Vise-Grips. It’s a flash picture and the worklight is a warm-white compact fluorescent: the color correction that makes the aluminum look neutral gray turns the reflected CFL into gold.

    Aligning replacement nuts
    Aligning replacement nuts

    I milled off the remains of the shell around the tapped hole, leaving a more-or-less flat bottom. If I cared enough, I’d machine a snug-fitting replacement aluminum plug, epoxy it into place, then (attempt to) drill-and-tap the hole again.

    Instead, because the hole was deep enough for a pair of 6-32 nuts and a washer, I simply aligned those on a screw and filled the hole with JB Weld epoxy.

    It doesn’t show in the picture, but the screw is well-lubricated with silicone grease to prevent it from becoming one with the nuts.

    I eased epoxy into the recess, chasing out the inevitable air bubbles, and then scraped off most of the excess.

    Epoxy fill
    Epoxy fill

    Let it cure overnight, scrub it on some sandpaper atop the sacrificial side of the surface plate, and it’s all good again…

    Sanded flat
    Sanded flat

    The little finger of epoxy sticking out to the front fills the end of the slit I carved into the top of the tap, which is visible in the other pictures if you look closely. The area around the hole isn’t stained; that’s smooth epoxy.

    Of course, the thermal conductivity of epoxy is a lot less than that of solid aluminum. I’m not really pushing the limits of TO-220 packages, so this kludge will work fine in this application. It’s also nice that the repair is on the bottom of the heat spreader, where nobody will ever know I screwed up…

    Now, to return to the project at hand, with even more motivation to avoid tapping holes in the future!

  • CPU Heatsink: Flattening Thereof

    I suppose I should have known better: the bottom of that heatsink wasn’t anywhere near flat. I think it mated directly with the top of the CPU through thermal grease, not a compliant pad.

    Curved copper heatsink surface
    Curved copper heatsink surface

    The obvious solution is to flycut the thing, which is where the Sherline’s limited Y-axis travel and teeny table put a cramp on your style. Normally, you’d put the length of the heatsink parallel to the X axis so the flycutter would clear on both ends, but there’s no obvious (read: quick and easy) way to clamp the thing that way.

    So I mounted it parallel to the Y axis, which meant I couldn’t get the flycutter completely off the near end. The first pass at Z=-0.1 mm, however, showed that not only was the surface curved, but it wasn’t parallel to the top of the fins (which were flat on the tooling plate). I suppose I should have expected that.

    This cut is has Z=-0.1 mm referred to the front end. It completely missed the other end:

    First flycut pass
    First flycut pass

    I flipped the heatsink around, measured the front-to-back tilt (about 0.16 mm), stuck a couple of brass shims under the front, and the second pass at Z=-0.05 mm from the new low point did the trick. Copper is nasty stuff and I did these cuts dry: the chips visible near the front are stuck firmly to the surface.

    Final flycut pass
    Final flycut pass

    I scrubbed both the heatsink and the spreader plate on some fine sandpaper atop the sacrificial side of my surface plate until they were all good. I can see the remaining flycutter marks, but I can’t feel them, and the plates slap solidly together with a pffff of escaping air:

    Flattened heatsink and spreader
    Flattened heatsink and spreader

    A dab of heatsink compound should work wonders; the maximum dissipation will be under 20 W, roughly comparable to that old K6 CPU, but now the heatsink will be contacting the entire hot surface.

  • Erasing a Hole

    Turning the plug OD
    Turning the plug OD

    The scrap pile disgorged a chunk of aluminum plate exactly the correct size for a heat spreader that will mate eight power FETS to that heatsink. The catch: a 1-1/4-inch deep hole tapped 1/4-20 for about 3/4 inch at almost the right spot along one end. Rather than sawing off Yet Another Chunk from the original plate, I figured it’d be more useful to just plug the hole.

    Note that this is somewhat different than the situation described there, where I screwed up by putting a hole in the wrong place. Here, I’m just being a cheapskate by making a piece of junk good enough to use in a project, rather than having it kick around in the scrap pile for another decade.

    Anyway.

    I turned a 3/8-inch diameter aluminum rod down to 1/4 inch for the threaded part and a bit under 0.200 inch to fit into the partially threaded end.

    A real machinist would single-point the thread, but I just screwed a die over it. The narrow end is slightly larger than the minor thread diameter, which helped get things started. Then a trial fit, saw off the excess on the skinny end, and apply a touch of the file to shape the end to mate with the hole’s drill-point bottom:

    Threaded hole plug
    Threaded hole plug
    Plug epoxied in place
    Plug epoxied in place

    I buttered up the plug with a generous helping of JB Weld epoxy and screwed it in. Toward the end of that process, the air trapped in the end became exceedingly compressed, to the extent I had to stop after each quarter-turn to let it ooze outward; eventually the hole gave off a great pffft as the remaining air pooted out. Unscrewed slightly to suck some epoxy back in, screwed it tight, and let it cure overnight.

    Squared-up block with plugged hole
    Squared-up block with plugged hole

    Sawed off the plug, filed the rubble more-or-less smooth, then squared it in the Sherline mill. The heatsink prefers to sit on a nice, smooth metal surface, so I flycut the other side of the block to get rid of a few dings and the entire anodized layer while I was at it.

    The epoxy ring doesn’t have a uniform width, because you’re looking at a cross section of the thread. The skinny part is the crest of the plug thread, the wide part is along one flank. Barely a Class 1A fit, methinks.

    New hole
    New hole

    Locate the midpoint of the block’s end, center-drill, then poke a new #29 hole 20 mm deep (I really do prefer metric!) for an 8-32 screw. The plug didn’t move at all during this process, pretty much as you’d expect. The chips came out of this hole in little crumbles, rather than the long stringy swarf from the solid aluminum on the other end.

    Using a simple peck drill canned cycle is just downright wonderful:

    G83 Z-20 R1 Q3 F100
    

    The rule of thumb is 3000 RPM with a feed 100 times the drill diameter. In this case, the drill is about 3 mm and calls for 300 mm/min, but the Sherline is happier with slower feeds. Maybe if I was doing production work, I’d push it harder.

    A real machinist would have a milling machine with a servo-driven spindle for rigid tapping, but I just screwed an ordinary hand tap into the holes.

    A bit of futzing converted a pair of solderless connectors into clips that capture the hooks on the ends of the heatsink’s springy wiffletree to secure the spreader to the heatsink. You can see the flycut surface peeking out from below the end of the heatsink. I should hit it with some fine abrasive to polish it out, but I think heatsink compound alone will do the trick.

    Heat spreader on heatsink
    Heat spreader on heatsink

    The next step: drilling-and-tapping eight more blind holes along the sides for the FETs. It’d be really neat to have a servo spindle…

  • Third Eye Hardshell Mirror Repair

    Alas, the mirror I installed this spring didn’t survive our bicycling vacation; it succumbed to the second of three stuff-all-the-bikes-in-a-truck schleps arranged by the tour organizers. Being that sort of bear, I had a spare mirror, duct-taped it in place, lashed it down with some cable ties, and we completed the mission.

    So.

    Back to the Basement Laboratory Plastic Repair Wing.

    The strut broke just behind the ball at the mirror, which implies the mirror plate got stuffed against something, rather bending the strut. The ball joint still worked, so I maneuvered the stub perpendicular to the mirror.

    Drilling the strut
    Drilling the strut

    Normally I’d try to re-glue the joint as-is to get the best fit, but past experience shows that if it breaks once, it’ll break there again. I wanted to put some reinforcement into the strut, not just depend on a solvent glue joint. Some rummaging in the brass tubing stock produced a 1/16-inch diameter aluminum (!) tube about 18 mm long: just what’s needed.

    So I filed the deformed plastic flat & perpendicular to the stubs, mounted the strut in the 3-jaw chuck on the Sherline’s table, lined the spindle up with the axis, and poked a 1/16-inch hole into the strut. The alignment looks decidedly off in the picture, but it’s actually spot on: what you’re seeing is some swarf clinging to the far edge. Honest!

    Then I grabbed the mirror plate in the 3-jaw, lined up on the stub, and drilled maybe 4 mm down, which was roughly to the middle of the ball. The tubing was a firm push-fit in the hole and I hope it won’t over-stress the plastic into cracking.

    Gluing the mirror strut
    Gluing the mirror strut

    Run the spindle up, remove the drill, grab the strut in the chuck (actually, I had to swap in the larger chuck first), dab some Plastruct solvent glue on both ends, align the strut with the stub (they’re actually square in that section), run the spindle down to ram the tubing into the strut, then a bit more to apply pressure to the joint. I made the total hole depth about 2 mm longer than the tubing, so as to avoid the embarrassment of having the ends not quite meet in the middle.

    No CNC; pure manual Joggy Thing action.

    Let it cure overnight.

    It’s now back on Mary’s helmet, with a pair of black cable ties ensuring that it won’t pop off, and seems to be working fine. I’m sure the ball joint will fail later this year, although that won’t be due to this repair.

    Mirror on helmet again
    Mirror on helmet again