Careful with That Desulfator, Eugene

September 19th, 2014 by Keith Neufeld

I’ve achieved some promising results from my battery desulfator / dewhiskerer / whateverer … and some less promising results.

overcharged 9-V / 7.2-V batteries

The smaller the battery, the more important it is not to forget that the desulfator / dewhiskerer is on. This was, as I recall, only about a fifteen-minute overdose. The magic smoke, I assure you, got out.

Subwoofer Voice Coil Failure Modes

June 9th, 2013 by Keith Neufeld

From the latest batch of reconing:

Three broken subwoofer voice coils

The left two are open — you can see the broken wire at the bottom of the left coil and the top of the middle coil. (As always, click for full-sized image.) The right one is shorted and I haven’t found where.

I find it interesting that these are wound with round wire and the replacements are wound with flat-cross-sectioned copper “ribbon,” to get more current capacity in the same vertical space.

$10 Razor E100 Scooter Project Day Two: First Battery-Charging Attempt

April 28th, 2013 by Keith Neufeld

Razor E100 battery and speed-control bucket

I tend to assume that batteries I happen upon will not be charged. Also that lead-acid batteries I happen upon will be low on water, even so-called sealed lead-acid batteries.

I wanted to start charging the batteries from my “new” scooter while working on other aspects of the project and the scooter didn’t come with a charger — I’ll deal with that later. Not knowing much about the wiring circuit yet, I didn’t want to connect an external charger to the batteries while they were still in-circuit and chance damaging the speed controller, so I needed to disconnect and remove them.

Wiggle wiggle wiggle <grunt> wiggle pull <grunt> WIGGLE WIGGLE BEND <grunt>

Wha?

Soldered battery clip

Who does this??? When they said solder the quick-disconnect terminals, they meant the wire side.

Fine. My uncle’s iron and a pair of pliers solved that problem.

Two sealed lead-acid batteries from Razor E100 scooter

Two batteries, extricated and not yet cleaned.

Prying open sealed lead-acid battery cover

In spite of being “sealed,” you can pry off the cover (preferably after cleaning, which I did first with Goo-Gone and then with dish soap and water)

Sealed lead-acid battery cell caps

and get to the cell caps, each with a little absorbent pad in case the cell venting carries too much moisture.

I could see no water in any cell of either battery. I borrowed a jug of distilled water from my folks (I don’t know why Mom always has some, but she does) and started filling them up … after taking measurements.

Battery 1 Battery 2
Initial 11.68 V 9.99 V
After adding water 11.62 V 9.92 V

I filled each cell, waited for air bubbles to trickle to the top, refilled, waited, refilled, waited … I’m guessing between the initial fill and while charging, I ended up putting at least 10 ml of water into each cell.

Then put battery 1 on my variable power supply with the voltage set to 13.8 V and the current limited initially to 0.1 A, raising the current limit to 0.3 A as it was clear that nothing horrible was happening. I checked on it every half-hour to hour, frequently refilling at least one cell in which I could no longer see any water.

After about four hours, it was up to 13.5 V. The water level in the cells had risen to overflow the opening and fill each reservoir. If I watched long enough, I could see the water in a couple of cells <pop>, indicating they were just starting to gas and it was time for me to stop this method of charging for the day. (More on that on a subsequent day, hopefully tomorrow.)

Charging sealed lead-acid batteries with power supply

While battery 1 was charging, I was also checking water levels in battery 2 and refilling low cells, just sitting on the counter.

Recalling that it had an initial 10 V charge to battery 1′s 11.7 V, noting that they had been connected in series, and knowing that the worst cell in a battery generally has a cascading failure, I expected a different charging experience from battery 2, and I was quite right.

I connected it to the power supply and it immediately showed 13.8 V at a 0.1-A current draw. Now, about an hour later, it’s at 13.5 V and 0.3 A and most of the cells have overflowed. It’s nearly done charging but I haven’t put nearly as much energy into it as I was able to put into battery 1 — that is to say, it’s not “taking” as much of a charge.

Battery 1 Battery 2
Initial 11.68 V 9.99 V
After adding water 11.62 V 9.92 V
After charging 12.68 V 12.48 V

Tomorrow, schedule willing, a load test and an attempt at desulfation.

$10 Razor E100 Scooter Project Day 1: Rear Wheel

April 27th, 2013 by Keith Neufeld

This afternoon I learned of the recently- (?) opened Deja Vu thrift store in Newton and made my first purchase: a Razor E100 scooter in considerable state of disassembly. I’ve long thought that electric scooters looked like fun …

Pieces of Razor E100 electric scooter

All of the wires are cut, the deck is missing, the rear wheel was unattached, naturally the drive belt was missing, and no charger.

$10. I bought it. Sounds like a fun project, eh?

Razor E100 scooter battery compartment

The battery and speed-control bucket could use some repair but seems at least functional. I started working on the batteries but as soon as my brother was available redirected my attention to reattaching the rear wheel.

Razor E100 scooter rear wheel, loose in forks

The rear wheel is belt-driven and needs to be positioned to align with the motor pulley but the spacers were absent and it slid freely from side to side.

Cutting a roll pin

A trip to the hardware store resulted in a roll pin with ID slightly larger than the 1/4″ axle diameter and length slightly greater than the two spacers needed, for $1.89. Then my brother’s giant chop saw made short work of creating two pieces from one.

Razor E100 scooter rear wheel, mounted

Touched up a bit on the bench grinder, ends rounded over with a file, and interiors cleaned out with a round file, spacers fit perfectly and the rear wheel bolts on securely. We “kicked” our way up and down the driveway and are eager to get the scooter powered up.

Next: Battery investigation.

Finding a Picture That I Took Used on eBay

January 6th, 2013 by Keith Neufeld

It is a bit surprising to follow a link from an eBay saved search and find a picture that I took.

Liebert UPS battery cable

The original is in this post from 2011.

I have no CC notices posted for the whole site (though I’d be happy to); but of course the Berne Convention provides for automatic copyright upon creation and publication of a work, so this is a blatant copyright violation.

Regardless, why is an eBay seller with only 110 feedbacks (vs one who does business on a scale of 110,000) too lazy to take their own picture of what they claim to have for sale?

Wanted: An EPROM Programmer that Works on a Mac

December 28th, 2012 by Keith Neufeld

And Linux. And old, high-programming-voltage EPROMs. And USB, naturally. If you know of such a thing, give me a shout in the comments — I can’t find any on Google, and I find plenty of links to other people who also couldn’t find them.

6502 Microprocessor, Apple ][, and Asteroids

A couple of weeks ago, I went to an annual holiday lunch with former coworkers and got to visit with an old friend. He was reminiscing about 6502 assembly programming on the Apple ][ and wondered whether I'd know where he could get one. I told him that I could probably loan him one or two; but (with a mischievous glint in my eye) that I have a couple of upright Asteroids arcade games and they run on 6502s and I’ve always wanted to reprogram one and write my own game.

Bump, set, spike. Yeah, he’s interested.

It’s not a completely impractical idea. I have a large schematic set that includes the addressing of the memory-mapped I/O and some rudimentary information on the operation of the vector generator board. There’s even a project to comment the disassembled ROM, which would give further hints about how to interface to the hardware.

If one were to undertake such a project, one would really like to use a USB-attached EPROM emulator so one could dump new code into the machine frequently and rapidly for testing and development. But at a bare minimum, one would need a stack of EPROMs and a programmer and ideally a ZIF-socket daughterboard to fit into the original EPROM socket and make it easy to swap EPROMs. As I have no Windows machines and do my electronics development on a synchronized fleet of Mac and Linux machines, a commercial EPROM programmer that I can use is going to be a little bit hard to come by.

Yes, I could run Windows under virtualization on my Mac; I think I may even be able to get a legal copy through my campus’s license agreement. But I’m not interested in going that direction unless I have to.

Isn’t it about time the world had a cross-platform EPROM programmer?

72G or Larger SCSI-2 Fast/Wide Hard Drives?

November 26th, 2012 by Keith Neufeld

Anyone know where to find new, large-capacity SCSI-2 fast/wide hard drives? A computer I supported at a hospital a long time ago has a failing hard drive and I’m happy to assist with replacement but I’m not coming up with any sources for the hardware.

New Arrival

September 3rd, 2012 by Keith Neufeld

computer

Yes, it is what it looks like.

I’m the second owner.

It hasn’t been powered on in 36 years.

I’ll post more pictures as I share the story and test it carefully to make sure it’s safe to power on.

OS X ATtiny25 Programming Walkthrough

July 7th, 2012 by Keith Neufeld

A while back I bought a batch of ATtiny25 microcontrollers and today I finally put one to use and got it programmed. MIT’s High-Low Tech group has put together a really nice package for programming ATtiny45s and ATtiny85s from the Arduino IDE, but it doesn’t support ATtiny25s, presumably because the limited memory doesn’t leave enough space after the bootloader is installed. I had a dickens of a time trying to find instructions to walk through programming an ATtiny25, much less on OS X; but it turned out to be pretty easy after pulling together a few separate resources. Here’s the path to blinkemness.

ATtiny25 board with USBtinyISP and Saleae Logic, overhead view

Read the rest of this entry »

Hand-Soldering SOIC

July 2nd, 2012 by Keith Neufeld

I wouldn’t want to do it for a living, but it’s an enjoyable diversion once in a while, particularly as a favor for a friend.

Breakout boards with SOIC

I aligned each chip’s pins by hand, clamped it to the board with a gator clamp (with heatshrinked jaws), soldered the far row of pins, rotated the board, and soldered the now-far row of pins.

Three rows I was able to do by blob-and-drag (heat the pins at the uphill end of the row, make a big solder blob, and drag it down the row at a pace slow enough to heat the pins but fast enough to keep the surface of the blob from oxidizing too badly, trusting surface tension to bring the blob with you and leave only a lovely solder fillet below each pin). Three rows I ended up doing slop-and-wick (get solder all over the place, then use “Size: Good” solder braid to remove solder bridges from between the pins, leaving a lovely solder fillet below each pin and evidence scorched flux everywhere).

I’d take recommendations on a good flux remover — preferably detailed recommendations indicating whether you have to scrub or just spray, how cleanly it washes off, etc. You can see that the rubbing alcohol I used leaves a bit of residue.