Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Tag: Improvements
Making the world a better place, one piece at a time
My bike helmet sports a mirror, microphone boom, and earbud, so I generally hang it from the top of the seat on my Tour Easy. There’s a convenient peg seemingly made for capturing the triangle of strap that normally goes over my ear and, up to the point where I set up this helmet, everything was good.
Helmet hanging on Tour Easy seat
After about a week, I noticed that the buckle was grossly off-center under my chin: the straps had shifted to one side.
Come to find out that the front strap on this helmet passes through an opening across the central member, below the plastic covering. Judging from the teardown of an older helmet, Bell used double-stick tape to hold the strap in place. Applying a constant force in one direction (I’m a creature of habit, the helmet always hangs from its right-side triangle) gently pulls the strap through the passage.
Front strap passing through helmet
So I cut two slabs of closed-cell foam and jammed them into the opening atop the strap, one from each side, with a screwdriver. That forced the strap against the adhesive and mechanically wedged it in place.
Setting relatively prime beacon times for the GPS-to-APRS trackers on our three bikes worked quite well, but I wondered how much better SmartBeaconing would be. The trick is getting the numbers right for typical bicycling speeds.
Here’s some settings (from the TinyTrack3+ config program display) that seem to work reasonably well…
SmartBeaconing Parameters
The general idea is to beacon every 10 minutes at rest and about three / mile in motion.
The only time I hit 3 MPH is up a really nasty hill, the likes of which I avoid with all due diligence. On the other end, 24 MPH is pretty much as fast as I can go for any length of time; faster, certainly, on downhills, but those are rare & precious commodities on most rides around here. The Slow and Fast parameters control both ends of that range. The beacon rate increases linearly below the Fast speed: 180 seconds at 12 MPH, which is roughly what I used for the constant-time setting.
Note that the Rate parameters are actually periods. Rate is thing/time, period is time/thing. The period varies as 1/speed, while the rate varies directly with speed. See the SmartBeaconing writeup or the TinyTrak3+ doc for the algorithm.
The Turn Slope parameter is the most confusing. It has units of degrees/MPH degree·MPH and serves to modify the Min Turn Angle so that you must turn more sharply at lower speeds to generate a beacon. This works better for vehicles with a wider dynamic range: our bikes tend to stay within 5-20 mph and a factor-of-four doesn’t affect the basic angle very much at all.
My track through a residential area shows pretty good “Corner Pegging” for those settings and, in any event, it’s much better than the simple every-three-minutes beaconing I’d been using before. On the other hand, this is in a low-RF-traffic area with a digipeater about a mile away across the Northway, so very few packets get clobbered.
APRS Track with SmartBeaconing
Perhaps setting Turn Slope to 240 degrees/MPH degree·MPH with a Fast Speed of 24 MPH and a Turn Angle of 10 degrees would be slightly better. At top speed the minimum turn angle would be 10 + 240/24 = 20 degrees and nose-pickin’ speed relaxes the angle to 10 + 240/6 = 50 degrees. On the other hand, that track looks pretty good as-is!
One problem with three bikes in close proximity (the track above is just me) is that we’ll all be turning at about the same time and, thus, sending beacons almost simultaneously. This will take a while to sort out, given that many beacons never make it to a receiver…
[Update:A correction shows why the units aren’t what I expected.]
I ran into an amusing situation on a recent family bike ride with our GPS-to-APRS trackers running: my ladies were transmitting a few seconds apart. As a result, I had to listen to a pair of very short data bursts in quick succession throughout the whole ride.
Under normal circumstances that doesn’t happen, because I set the TinyTrak3+ trackers to delay during and wait a second after a voice PTT that collides with an automatic beacon. Somehow they never managed to delay an APRS beacon to knock the synchronization off kilter.
So I tweaked the automatic transmission intervals to make us relatively prime: 179, 181, and 191 seconds. That’s close enough to the original 180 seconds as to make no difference, while now ensuring that we won’t collide with each other for very long even if we should get aligned.
An alternative is SmartBeaconing, which I’ll turn on in a while after I collect a bit more data.
If you have some spare CPU and power, you can join the Great Internet Mersenne Prime Search and help find new primes, albeit ones much larger than I need…
The remote cable for the Yaesu FT-857 I have in the car terminates in an 8-pin modular plug. The connector body has a cutout for the round rubber (?) insulation around the cable; it’s not set up for a standard flat 8-wire network cable. However, the cable makes a right-angle bend immediately outside the Front Panel to fit inside the confines of the remote mounting case, which pulled the insulation out of the connector.
Connector with displaced insulation
The electrical connections are fine, but that can’t last. I finally got around to armoring that bend to (I hope!) prevent any problems. Contrary to what you might expect from my proclivity to blob epoxy on everything, I blobbed on hot-melt glue to hold the wires in place, as well as turn a bit of the cable into a rigid body. Even in a hot car, this ought to work fine…
Connector with hot-melt glue
I put some ordinary adhesive tape on the back of the Panel, butted up against the connector body, to keep the glue out of the socket and off the (back of the) Front Panel. That prevents the connector from becoming one with the Panel.
Pause while the glue solidifies, release the latch and pry the connector+glue off the tape with a small screwdriver, trim the excess glue, then peel the tape off the Panel. The connector snaps into place just like it should and the wires no longer have any freedom of motion.
Here’s what the modified connector looks like in all its glory. The cable really does bend downward slightly beyond a right angle in order to fit into a recess in the Front Panel.
Finished connector kludge
This isn’t suitable for a connector getting a lot of the old in-out in-out, but the Front Panel remains in place for months at a time and this should delay the inevitable failure.
Mary’s feet are exquisitely sensitive to irregularities in the insoles of her shoes, which poses a real problem with her bike shoes: those SPD cleat recesses are no good at all.
This is a view down into one shoe, with the SPD cleats adjusted all the way to the rear. That leaves a large recess in the front, which was painfully obvious to her sole. The white shape is the gap filler…
I pressed a sheet of paper across the gap to get the general shape, traced it twice onto a slab of 0.060-inch aluminum with a nice pebbly paint job, and cut the two pieces out. A few conversations with Mr Belt Sander, a few licks with a rat-tail file, and they dropped right onto place. The recess is slightly curved, but I didn’t have to bend the pieces to fit.
I laid duct tape across the whole affair, put the insoles back in place, and it was all good.
The backing plate is 0.072 inch thick and she was content with the difference.
In previous shoes, with the cleat near the middle of the adjustment range, I’ve stuffed epoxy putty into the gaps. That works, but it doesn’t bond to the (miracle engineering plastic) soles and tends to crumble. This is Not A Good Thing…
This is a tweak to the previous design, based on some road testing.
An attenuator on the output of the MAX4467 voice amp allows gains below unity. Right now, the MAX4467 has Av=5 and the attenuator cuts it back by about 1/5, so the overall gain is about unity. I have a bunch of surplus electret mic capsules and some have come through really hot; this allows backing the gain way down with the mic amp set to Av=1.
That requires stiffening the Vcc/2 supply by swapping in a 33 µF cap for the original 1 µF unit. If you don’t do that, the amp turns into a oscillator: the attenuator jerks the Vcc/2 supply around, which feeds back to the non-inverting input of the MAX4467. In principle, the gain should be less than unity, but I wouldn’t bet on it.
The MOSFET relay sometimes didn’t quite turn on from the piddly 4 mA available through the ICOM IC-Z1A’s mic power supply; it was vaguely temperature dependent. I returned to an ordinary optocoupler with a CTR of about 100% driving a 2N2907 PNP transistor, as in the first-pass design that you never saw.
The two 2N2907 devices allow either a through-hole TO-92 or SMD SOT-3 package, depending on what you have and the power dissipation you need. In my situation, the SMD version suffices, with less than 100 mV of VCE saturation.
Let me know if you need the Eagle PCB files or PCB layouts.
[Update: I’m not convinced the Vcc/2 supply is stiff enough. I ripped out the attenuator and cut the amp gain to 1.0. If I get some really hot capsules, I’ll think it over a bit more.]
I’ve managed to lose enough weight off my butt (it doesn’t go away, it just becomes leg muscle for a few months) that I must move the seat on my Tour Easy forward maybe 5 mm. Alas, I’ve run out of adjustment room: the frame is a Medium Large and I probably should have gotten a Medium; that decision was forced by getting a much-too-small Linear many years ago.
The general idea here is to bolt the seat to an aluminum circumferential clamp just forward of the plate and tubes that normally secure the seat to the frame. That moves the clamping bolts about 15 cm forward, but they slide in slots along the seat bottom.
The bolts are 1/4-20 stainless carriage bolts, with the square shank under the head sliding in those slots. I think the clamp can be about the same thickness as the existing tubes, so the same bolts will work.
The main frame tube runs slightly above the two small tubes that stiffen the rear triangle. It’s not clear those clearances in the clamp must be contoured to fit the tubes exactly; a simple flat cutout will probably work just fine.
The top of the clamp must have two bosses to support the seat base around the clamping screws. A line of rivets down the middle secures the seat base to the contoured (carbon?) fiberglass pan holding the foam cushion.
The Smell of Molten Projects in the Morning 