The Smell of Molten Projects in the Morning

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

Author: Ed

KG-UV3D GPS+Voice Interface: APRS Bicycle Mobile

Wouxun KG-UV3D with GPS-audio interface

Both of the GPS+voice interfaces for the Wouxun KG-UV3D radios have been working fine for a while, so I should show the whole installation in all its gory detail.

If you haven’t been following the story, the Big Idea boils down to an amateur radio HT wearing a backpack that replaces its battery, combines the audio output of a Byonics TinyTrak3+ GPS encoder with our voice audio for transmission, and routes received audio to an earbud. Setting the radios to the APRS standard frequency (144.39 MHz) routes our GPS position points to the global packet database and, with 100 Hz tone squelch, we can use the radios as tactical intercoms without listening to ~~all~~ much of the data traffic.

The local APRS network wizards approved our use of voice on the data channel, seeing as how we’re transmitting brief voice messages using low power through bad antennas from generally terrible locations. This wouldn’t work well in a dense urban environment with more APRS traffic; you’d need one of the newfangled radios that can switch frequencies for packet and voice transmissions.

So, with that in mind, making it work required a lot of parts…

Tour Easy – KG-UV3D GPS interface

A water bottle holder attaches to the seat base rail with a machined circumferential clamp. Inside the holder, a bike seat wedge pack contains the radio with its GPS+voice interface box and provides a bit of cushioning; a chunk of closed-cell foam on the bottom mostly makes me feel good.

The flat 5 A·h Li-ion battery pack on the rack provides power for the radio; it’s intended for a DVD player and has a 9 V output that’s a trifle hot for the Wouxun radios. Some Genuine Velcro self-adhesive strips hold the packs to the racks and have survived surprisingly well.

Just out of the picture to the left of the battery pack sits a Byonics GPS2 receiver puck atop a fender washer glued to the rack, with a black serial cable passing across the rack and down to the radio bag.

A dual-band mobile antenna screws into the homebrew mount attached to the upper seat rail with another circumferential clamp. It’s on the left side of the rail, just barely out of the way of our helmets, and, yes, the radiating section of the antenna sits too close to our heads. The overly long coax cable has its excess coiled and strapped to the front of the rack; I pretend that’s an inductor to choke RF off the shield braid. The cable terminates in a PL-259 UHF plug, with an adapter to the radio’s reverse-polarity SMA socket.

The push-to-talk button on the left handgrip isn’t quite visible in the picture. That cable runs down the handlebar, along the upper frame tube, under the seat, and emerges just in front of the radio bag, where it terminates in a 3.5 mm audio plug.

The white USB cable from the helmet carries the boom mic and earbud audio over the top of the seat, knots around the top frame bar, and continues down to the radio. USB cables aren’t intended for this service and fail every few years, but they’re cheap and work well enough. The USB connector separates easily, which prevents us from being firmly secured to a dropped bike during a crash. I’d like much more supple cables, a trait that’s simply not in the USB cable repertoire. This is not a digital USB connection: I’m just using a cheap & readily available cable.

All cables converge on the bag holding the radio:

Tour Easy – KG-UV3D + GPS interface – detail

Now you can see why I put that dab of white on the top of the knob!

The bag on my bike hasn’t accumulated quite so much crud, because it’s only a few months old, but it’s just as crowded:

KG-UV3D + GPS interface on Tour Easy – top view

This whole “bicycle mobile APRS system”, to abuse a term, slowly grew from a voice-only interface for our ICOM IC-Z1A radios. Improving (and replacing!) one piece at a time occasionally produced horrible compatibility problems, while showing why commercial solutions justify owning metalworking tools, PCB design software, and a 3D printer.

I long ago lost track of the number of Quality Shop Time hours devoted to all this, which may be the whole point…

In other news, the 3D-printed fairing mounts, blinky light mounts, and helmet mirror mounts continue to work fine; I’m absurdly proud of the mirrors. Mary likes her colorful homebrew seat cover that replaced a worn-out black OEM cover for a minute fraction of the price.

2012-09-11
Vanagon iPod Interface: Minimal Edition

My buddy Duggles, from far-off NH, restored his ’83 Vanagon to its original hippie-chick-magnet state. Late in the process, he realized that the once-fancy CD+radio widget in the dashboard lacked a line input for his iPod / iPad / iDingus. Knowing my foibles, he asked for advice.

Fortunately, he’d already discovered the service manual, without which life is always much more difficult. Search for PIONEER DEH2850MP SERVICE MANUAL and pick the site you prefer.

My first email went a little something like this, with a few updates:

BEH2850MP Audio Mux

The trouble with jamming a new line input into the existing circuitry is that you must match the DC levels as well as the audio amplitude. The schematic on page 19 shows the selector IC has capacitor-coupled inputs and outputs to strip off the DC level.

It would be very easy if the multiplexer (IC151, top of page 19, detail shown) had separate control inputs that we could override, but it uses a serial control stream from the CPU. No practical way to mess with that, alas.

As nearly as I can tell, the best way to do this would be to hack a DPDT switch between the FM/AM tuner and the amp, upstream of the mux. You pick the Radio input, flip the DPDT switch, and the iDingus plays through the Radio inputs.

However, an easier way is to simply inject the iDingus audio in parallel with the tuner audio, but set the tuner to an FM frequency without a radio station. The radio output should mute, leaving the field clear for the iDingus audio. This might not work, but it’ll be dead simple to try. If it’s acceptable, then you’re done.

The obvious problem is that we don’t know if the iDingus line level matches the tuner’s line level. The mux is upstream of the volume settings, so there’s hope that this will all Just Work. If it’s way too loud, that’s fixable. If it’s too soft, that’s a problem.

So, to begin…

DEH2850MP PCB Radio Jumpers

The diagram on page 36/37 shows the A side of the PCB, with all the connectors & suchlike. The FM/AM Tuner Unit is over along the right side, with the audio output on pins 23/24 near the bottom and ground on pin 22. The traces proceed upward along the edge of the PCB, cross the connector near its middle, the audio passes through caps C151/152 on the B side, go through two jumpers on the A side across a mess of traces, and then dive to the B side and wriggle into the IC151 mux.

Quite conveniently, the ground trace follows along with them and is the lower of the three traces just to the right of the mux.

If I interpret the part number for C151 correctly (page 45, top right):

C 151 ... CKSRYB224K10

it’s a 220 nF cap. Anything around that value should work. This one from Radio Shack is grossly overpriced; anything with the same or larger value is OK (voltage rating doesn’t matter): NTE MLR224K100 – 0.22MF 100V Mylar Capacitor

Solder one lead of each cap to the top two jumpers, solder suitable wires to the other cap leads, solder the ground / shield wire to the bottom jumper, solder a suitable jack to the cable, plug iDingus into jack, fire that mother up, and see what happens.

The right channel is on pin 24, which goes to the top jumper of the three. Don’t bother trying to figure out which pin of the iDingus corresponds to that channel; just solder the damn wires and fix it later if it’s wrong enough to be objectionable.

I have no idea where or if you can drill hole(s) to snake the cable(s) through the housing. If the Vanagon doesn’t have a rear power amp, you could probably cut the traces under those RCA jacks (CN352, top right on page 37, above the FM/AM tuner) and repurpose them.

Give it a go…

We both attended Lehigh U, but Duggles realized early on that he lacked the personality flaws common to engineers and bailed out before damaging himself too badly. So his reply didn’t surprise me in the least…

I read your instructions carefully, examined the kindly supplied circuit diagram, and pored over the circuit boards with a magnifier. Then I blew you off (!!), threw caution to the winds, hacked off an old headphone cord, snaked the wires in, and soldered right to the very convenient L/R outputs on the RF board. Fired it up ,,, shitz, tons of background hiss, no quieting on the FM signal! A skein of obscenities was loosed in the mountain air until I thought to turn the iThang on … boom, full quieting, no hiss, and a quite substantial sound. No level issues at all, quite clean and detailed, and I didn’t even use the capacitors! (What was their purpose btw?)

After observing that a prophet is not without honor, save in his own land, I couldn’t resist going full-frontal didactic again:

The mux has a DC bias on its signal lines, with caps on both the input and output to isolate it from the surrounding circuitry. Back in the day, analog switches were fussy about their DC bias, so you had to go overboard to make them work at all.

I don’t know if the iDingus also has DC blocking caps on its output and figured that injecting raw DC from the mux into its guts could be a Bad Thing. But, eh, those engineers at Apple (‘s contractor) are smart folks and (probably) anticipated this sort of (mis)behavior.

The hiss you get with the iDingus turned off probably comes from dragging the mux bias to ground. I don’t know that’s a Truly Bad Thing, but adding those caps should eliminate any future problems.

You could even play DJ by combining radio & iDingus audio!

Rock on…

Seeing as how Duggles actually was a DJ for quite some years, I wouldn’t be surprised in the least to hear he does exactly that. We’ll be visiting him later this Autumn and I’ll inspect his work.

I love it when a plan comes together…

2012-09-10
Hummingbird Moth!

A Hummingbird Moth recently visited the Butterfly Bush:

Hummingbird Moth – left side

They’re heavy-bodied moths and, unlike those butterflies, never alight on the flowers to dine. Their wings are clear and never stop moving:

Hummingbird Moth – wing

It’s impossible to not see a face looking back at you, even though that’s a proboscis down the middle:

Hummingbird Moth – front

They don’t stay very long and are extremely flighty, so the picture are catch-as-catch-can: hand-held with the DSC-H5, roughly dot-for-dot crops, and only the last one got any color correction. I didn’t have time to set the usual one-stop underexposure, so the colors washed out a bit. I really like the first picture; almost all my mistakes canceled out.

2012-09-09
Painted Lady Butterflies

Painted Lady butterflies seem to be spreading northward, along with the Giant Swallowtails, and three visited the Butterfly Bush at the front window:

Painted Lady – dorsal

The underwing shows four eye spots as distinguishing features:

Painted Lady – underwing

Painted Ladies have odd-looking “faces” on their front end:

Painted Lady – front

The proboscis works wonderfully well on deeper flowers than these, but they’re not passing anything up:

Painted Lady – proboscis

Another view:

Painted Lady – right side

The refueling tube stows neatly for flight:

Painted Lady – proboscis curled

One had a few notches taken from a wing:

Painted Lady – left rear

You can’t ask for prettier colors:

Painted Lady – right front

These are all hand-held with the DSC-H5 wearing the 1.7 teleadapter, underexposed by 1 stop to keep the dark background from burning out the butterfly colors. The images are very close to dot-for-dot crops from much larger pictures, with a touch of unsharp mask, and no color fiddling at all; bright daylight and a gorgeous subject come out beautifully!

2012-09-08
Wouxun KG-UV3D Volume Knob: More Black on Black

The volume / on-off control knob on our Wouxun KG-UV3D radios has the most minute raised dot you can imagine to mark its orientation. Yes, it’s another subtle black-on-black control! See if you can spot the dot:

Wouxun KG-UV3D – volume knob marking

The radio lives in a small pack attached to the back of the seat frame: we turn it with a fingertip and adjust the volume by touch; the dot is just barely perceptible to my finger. Nevertheless, WIBNI (Would It Be Nice If) you could look at the knob from a distance and determine whether the radio was turned on?

A dab of typewriter (remember typewriters?) correction fluid later:

Wouxun KG-UV3D – garish knob marking

Not elegant and sure to wear off after a while, but the smudge should remain visible forever.

2012-09-07
Compact Fluorescent Bulb Lifetime: Another Data Point

Each of the three chandeliers in the Poughkeepsie Train Station sports 36 bulbs in two rings. When the station opened in 1918 they installed those newfangled incandescent bulbs that were all the rage at the time. The color of the bulbs in this Wikipedia picture, dated October 2007, suggests that tungsten ruled for at least nine decades:

Poughkeepsie Train Station Interior

Since then, they installed chunky compact fluorescent bulbs that probably provide the same amount of light, minus the pinpoint highlights from tungsten filaments in clear bulbs. This view from below the central chandelier shows the layout and some detail of the carving & decorative sockets:

Pok RR Station Middle Chandelier – detail

In addition to being decorative, those chandeliers also give useful data on the reliability of compact fluorescent bulbs. With the contrast stretched the other way to make the bulbs easier on the eye, count the number of deaders in …

Chandelier 1:

Pok RR Station Chandelier 1

Chandelier 2:

Pok RR Station Chandelier 2

Chandelier 3:

Pok RR Station Chandelier 3

I took each picture from a vantage point showing all the deaders; the bulbs hidden behind the central dingus work.

Let us assume all 108 bulbs were installed at the same time and, given the number of deaders, haven’t been touched since then (although they’re not covered in fuzz, which suggests that they’ve been dusted within living memory). I was there in mid-afternoon, so the bulbs probably burn 24 hours/day and aren’t subject to early failure from frequent starts.

So, in no more than five years, 108 CFL bulbs have a 4.6% failure rate, which works out to 0.9%/year, more or less, ignoring any infant mortality. If they’ve been up there for the last 2.5 years, then it’s 1.8%/year. Replacing deaders since installation, of course, makes it worse than that.

Over the course of a decade, a compounded 0.9% failure rate will kill 9.4% of the bulbs. After 20 years, 20% will be dead. A 1.8% annual failure rate kills 20% and 43%, respectively.

Now, I’ll grant you that tungsten bulbs burn far more energy over that time, but replacing a percent or two of those complex and somewhat eco-hostile CFL bulbs every year cuts away a big chunk of the rainbows-and-pink-unicorns delight involved in Saving The Planet.

2012-09-06
NYS DOT Repair Quality Control

The paving along Rt 376 just south of Raymond Avenue developed transverse ridges; evidently the old concrete roadway below the more recent asphalt cap is shifting. Bumps in the travel lane are not to be tolerated, so they milled off all the ridges. Problem solved!

Of course, the remaining asphalt isn’t thick enough to withstand any stress and promptly crumbles:

NYS DOT joint milling quality

Although the shoulder may appear to be wide enough for bicycle traffic, the debris strewn along it makes for a perilous journey: the larger chunks are bigger than my fist. Several of the milled joints along the unimproved section of Raymond and that stretch of 376 are disintegrating, so it’s not like they got just this one wrong.

Doesn’t bother the DOT one little bit, because their idea of a “shared use facility” is a sign with a picture of a bicycle, labeled Share The Road. As long as the travel lane seems mostly passable by automobiles, their job is done.

2012-09-05