Cort’s troubleshooting a new repeater installation out by Lecompton and sent me this picture of his adorable new RF wattmeter. (For the record, Cort calls it “old school” rather than “adorable,” but what does he know.)
He bought it from the Chuck Martin RF Shop, which he highly recommends.
Here’s the first batch of stuff from Slim’s “Dump” — rackmount equipment that I can’t identify as being associated with anything else from out there.
I can’t tell that any of this stuff as still useful (which presumably has something to do with why it was out in the Dump in the first place), so it’s destined for disassembly, component removal, case reuse, and recycling. If there’s anything that strikes you as useful, throw a comment down below about what it’s good for, offer to pay me what it’s worth to you plus shipping costs, and I bet we can work something out. I’d love to see some of it go to someone who’d actually make use of it.
Last weekend, Cort and I went to Pittsburg to help Slim‘s wife go through his mounds of AV gear and electronic parts. A couple of guys from the amateur radio club joined us, and we spent Friday night and most of the day Saturday identifying and sorting things.
For all that effort, we basically got the van cleaned out and the family room counter cleaned off. We could tell we’d made a dent, but there’s obviously a huge amount left to do. Nevertheless, Maeve was overjoyed at the work, and I think the most important thing we accomplished was helping her reduce how overwhelming the job seemed to be. Plus I got her DVD player, worldwide and NTSC-only VCRs, and Tivo hooked up to her TV so she can watch movies again.
As we sorted, we grouped things into six rough categories:
Each of us took home a few things, and I have others to talk about in due time; but the one that impresses me most was Slim’s prototyping station. Cort often talks about how important it was to Slim that people use things and how ready he was to give things away to people who would actually use them.
The radio guys aren’t really building things these days; Cort said that he and I are the only ones doing circuit design, with me doing the most right now. Because of that, Cort insisted that I be the one to take the station. I am very honored; and with great honor comes great responsibility.
Slim designed and built this himself. To me, it not only is a very impressive piece of work, but also reflects a lifetime of experience prototyping circuits and knowing what features are useful to have at hand. A station like this should come with a manual, and it’ll take me some time to figure it out and become fluent with everything it offers.
Starting at the top, the station has a multitude of connectors: DB-25 male and female, a card-edge socket that reminds me of my VIC-20 days, 1/4″ and 1/8″ jacks, barrier strip, RCA, BNC, and binding posts.
Each connector breaks out to well-labelled wire sockets in an area near the left of the front panel. These pin sockets are a Slim signature item — he used them on all of his breakout and prototyping stations, and I’ve never seen them anywhere else.
Next to the connector area, in the right of the photo, is an area for a signal generator that looks like it wasn’t finished. Based on some conversations I had with Slim about signal generators, my guess is that he intended to take the board out of a commercial unit, embed it inside the case, and extend its controls to the front panel, rather than construct his own from scratch.
At the far left of the front panel are power supply connections providing variable + and – voltages and dual +5V supplies. If I’m following correctly, the two 5V supplies run to the ends of the rail above the breadboards, and are jumpered down to the left and right breadboard sections from there.
In the upper center are two six-digit sets of seven-segment LEDs. The lower set appears to be broken out for matrix drive (labelled Digits 1-6 and Segments a-g at the left), and the upper set appears to have integral decode/drive (individually labelled A-D and Dp under each digit). There’s also a set of sixteen LEDs for individual use.
The upper right corner has a microcomputer section with a 24-pin ZIF socket for EPROMs, selectable between 2708 and 2716 (this is old school) and presumably a microprocessor hidden behind the panel. Given the PIA labels, I’d guess it’s a Z80, but it could be something else with an external PIA chip as well.
That’s all the closeup pictures I took, but there are a few more features I’ve already figured out. The row of black knobs across the center are potentiometers of commonly useful values, broken out to pin sockets underneath each one. The row of tracks between the pots and the breadboards delivers power and also has four buses labelled A-D.
Above the tracks are wire sockets for the switches and pushbuttons across the bottom of the case. There appear to be six logic inverters. And at each end are two sets of LEDs labelled H (red), L (green), and P (yellow) — I assume logic probes showing high, low, and pulse.
And of course a breadboard, generously sized, with a bunch of parts still on it. It has a couple of TL064s, Slim’s and Cort’s favorite op-amps, but it doesn’t look like it’s really a circuit in development. It looks more to me like it might be leftover parts that he was moving out of the way.
My challenge now is to learn to use it effectively. I always have enough clutter on my workbench that I have preferred using small breadboards and pulling out only the parts and connectors I need at the moment. On the other hand, the benefit of a prototyping station like this is always having everything at hand, saving the time of having to dig out the right connectors and displays.
It’ll definitely take some to get used to, and to determine which method really works best for me. Maybe eventually, it’ll inspire me to build my own comprehensive station that’s just right for me; and with Cort’s help, hand Slim’s station down to the next generation of experimenter.
Here’s a project that I’ve been kicking around for a long time (three years–I guess that’s not so long compared to some of my projects 
) and finally built–a battery meter. My friend/enabler Slim Cummings in Pittsburg gave me a couple of surplus 3-1/2 digit, .2V panel meters, and I thought they’d be perfect for testing the freshness of AA and AAA cells.
The meter was the inspiration for the project. It has a 3-1/2 digit (a 1 plus three 7-segment digits–1888) display, a configurable decimal point, and an Intersil ICL7106CPL LCD/LED Display, A/D converter chip. You give it 9V supply, a jumper for the decimal point, and a voltage input; and it samples the voltage and drives the LCD. It’s a very nice package that just begs to be used for something interesting.
The physical aspects of the project actually took much longer than the electrical. First off, I wanted to find a case with the following characteristics:
I figured I’d find a plastic project case from Radio Shack with a 9V holder in one end and enough room for everything else to fit . . . no such luck. I figured I’d find something in my junk bin that I could reuse–I was coming close with some old and broken copper-to-fiber media adapters, but they weren’t quite right. Finally I stumbled across the idea of using the plastic case from a data backup tape, and I rummaged around until I found this KAO 8mm data cartridge case.
I’m not wild that it’s translucent–I don’t like seeing the guts of things when I’m using them–but it’s the perfect size. The meter exactly fits across the width, the 9V battery exactly fits in the thickness, and it’s in portrait format. Plus I guess it’s kind of cute opening the case like a cassette case to change the 9V battery.
I picked up a single AA battery holder at Radio Shack a couple of weeks ago, and had to mod it a bit to fit it onto the case the way I wanted. The leads originally routed out holes in the ends of the holder, but I wanted them to go straight down through the case. Fortunately, there was already a hole underneath the terminal at each end (you can see the one at the right end of the above picture), and I was able to fish the wires through and tug them into position to make it work.
The holder also had tabs curving slightly around the front, to help hold the AA cell inside. Since I want to be able to insert and remove cells quickly, I removed the tabs by scoring the plastic flush with the rest of the front of the holder, then snapping them off. I also confirmed at this point that a AAA cell would make contact with both ends of the holder, even though it wouldn’t be held as securely. (AAA cells are shorter than AA cells, as well as thinner.)
I drilled mounting holes in the case for the meter and battery holder, as well as holes for the wires to go through. The plastic was so soft, I didn’t even bother chucking the bits into my drill for most of the holes–I just turned the bits a few rounds with my fingers and I was through the case.
I did get to use my stepped drill bit set to enlarge the meter’s mounting holes–the bezel’s posts have larger-diameter plastic shoulders at the base, my mini-drill doesn’t have bits that large, and the stepped drill bits do an excellent job of enlarging while remaining concentric with the pilot hole.
The last tricky bit of work with the drill was the big ugly hole in the center of the picture of the drilled case. I needed a power switch for the meter, but I was loath to have to have to slide a switch or press a button every time I wanted to use it–I wanted it to spring to life when a cell was inserted to test. Plus for reasons to be described a bit later, I planned for a pushbutton on the front already, and I didn’t want to have two.
The solution was simple enough–a pushbutton switch inside the battery holder, actuated by the insertion of the cell itself. I salvaged a tiny microswitch (“nanoswitch???”) from a dead CD-ROM drive (a limit switch from the optical sled), reamed much too large a hole in the case and battery holder, poked the switch in from underneath, and hot-glued it in place.
The meter board is built for a range of 0 – .1999 (.2) V, but has pads to set the placement of the decimal point and to provide your own voltage divider to adapt for other ranges. The documentation gave the resistor values to adapt for 20V and 200V, from which it was easy enough extrapolate the nominal values for 2V operation: 9MΩ and 1MΩ. Well, I have 1MΩ resistors on hand, but not 9MΩ, and certainly not precision.
Fortunately, 9:1 ≅ 10:1.1, so I put a 10MΩ resistor into the pads for RB (upper left) and chained a 1MΩ and a 100kΩ in series between the pads for RA. (Those lap-soldering skills from a summer of module assembly at IFR Systems do come in handy.) Also fortunately, the calibration potentiometer had a generous range, so I was able to work around the 1% difference from the nominal ratio.
I also guessed (correctly) that the proper position for the decimal-select jumper was P1, which was missing from the voltage range chart.
I had one more set of components to add, but I couldn’t resist wiring it up to see how it worked so far.
I soldered the 9V battery clip’s ground lead to the ground connection at the lower left of the meter board, the positive lead to the microswitch glued into the AA holder, and the normally open (NO) lead from the microswitch to the supply connection on the meter. I also soldered the AA battery holder’s leads to the Vin connections at the upper left. If you look closely enough, you may see that I just tack-soldered them in place with a lot of exposed wire a the end; I plan to come back and organize the wiring more carefully, and didn’t take a lot of extra effort at this point.
And it works as planned! Not that there was much surprise, but it’s still nice when a project comes together. I was also pleased that the (undocumented) position of the decimal point was correct. Further, I was hoping to avoid cutting a large hole in the box for the panel meter; and I find it adequately legible reading through the nearly transparent case, without a hole.
I put a AA cell into the holder, the switch activated beautifully, the meter sprang to life, and I had a reading of the AA cell’s voltage. I measured the cell’s voltage in situ with my best voltmeter, calibrated the panel meter’s reading via the potentiometer on the back, and measured with my good meter once more to make sure the voltage hadn’t drifted while I was adjusting. Good enough!
Finally, I drilled two more small holes in the case, poked a pushbutton switch through (in the lower left of the above photograph), and wired a 10Ω resistor in series with the switch, and the switched resistor in parallel with the AA holder. From my first inspiration for this project, I’ve wanted to be able to test cells under load as well as unloaded. I find that some cells I’ve owned–particularly, I believe, when they’ve lost capacity due to age rather than use–will show a relatively high unloaded voltage even though they have very few mAh left. I very specifically wanted to be able to test under load to identify this condition.
And it’s proved itself already. The cell shown under test reads 1.163V, which is by no means new, but might still appear to be usable in some types of devices. But when tested with a load, it drops immediately to ∼.8V and continues to fall toward .7V–not nearly as promising. In contrast, another cell I’ve tested measured ∼1.2V unloaded, but still ∼1.1V under load–very likely quite usable yet.
I’ve already switched to using NiMH cells for all my projects and consumer hardware, but I have a number of alkaline AA and AAA cells around the house from the old digital camera and the Visor PDA, with no good idea which are fresh and which need to be discarded. (Y’know, it’s such a pain to test cells with a voltmeter and only two hands.) I can finally conveniently test and sort them into four categories:
I’m planning to build a “Joule thief,” a clever and tiny transformer feedback single transistor inverter that claims to be able to “provide a week of continuous low level light from a battery that would normally be considered dead.” Maybe I’ll end up with a bunch of “electronic candles” sitting around for the next ice storm; who knows.
Update: Here’s another Joule thief project.
A huge thank-you to my friend Slim, who gave me the panel meters that started this all; and who’s always generous with his vast experience and equally vast stores of electronics surplus.