Auto Call Box This is something I felt the need for pretty early on. There are different ways of making this happen on some controllers but I really wanted something universal to run the car for me while I’m doing something else.
The first one was all analog with just one relay. One call on the N/O and one call on the N/C. Just cycled on/off with an adjustable timer. This worked fine on some controllers but a lot of relay logic equipment doesn’t like for a call to be held while it’s trying to be cancelled. Relays chatter, resistors get hot, etc.
For the second one I had to use a microprocessor to make a proper 2 relay box with adjustable “on time” (time the relay is picked to place the call) and adjustable “off time” ( time between relay picking to place the call. Nice thing about this one is it’ll run for days on a 9v battery.
Then this is the most recent version with 5 solid state relays. It can do random or sequential calls and adjust the number of relays used in the cycle. The battery doesn’t last as long as the previous version though. It’ll run off the battery all day for troubleshooting but to run overnight it has to be plugged into power.
I wrote the programs, designed the board in KiCad, and made the board at home using toner transfer. If I made it again though I’d just send the Gerber files out and have the PCB made. It’s cheap and the quality is excellent.
The 6 x AA batteries are about 9vdc so I used 3 x 3.6vdc cells instead to make room for the power jack and transfer relay. So it runs off the batteries through a step-down regulator until a 9v external power adapter is plugged in. Here's a diagram.
Ya that’s cool, I was thinking about trying to make one with a rechargeable battery. As long as it could run continuously with the charger plugged in. Cool thing with those meters is you can buy the back assembly and just swap them out.
Well I made the rechargeable version of the Fluke 289 battery. 5ah is the biggest li-ion battery I could find to fit so it’s about 30% less capacity than the last version. 1 cheap board from Amazon pretty much does it all though so that’s nice. It becomes obvious pretty quickly that you really need an indication of the charge on the battery to be useful so I made a little board to do the job. Rechargeable 289 Pics
It's good to see the younger guys thinking outside the box. It has been a long time but years ago, I made a few gadgets pertinent to what I was working on. Otis B base (goolean logic) was a early digital design that revolved around discreet DTL (yes...diode transistor logic). It could be a total beast to troubleshoot. You might have 4 or 5 inputs forming the conditions for as an example perhaps generating a door open pilot. Rather than fight the limitations of a single logic probe, I built a custom unit which had 5 inputs. I used mostly 2N222 transistors and red and green leds for a "high " or "low" state. You could label an entire complex logical circuit and monitor it without the hassle much less danger of shorting out a backplane mishap with a single logic probe. This same circuit also worked well on the Haughton 1092 IC controller. A similar early digital controller that was based off of TTL circuits.
The other circuit was built to help troubleshoot intermittent drive trips on a Sweo DC drive. Since the fault leds didn't latch, often you had no idea of why the drive had tripped. So I built a circuit with 4 window comparators based off LM3302 opamps, a quad Schmidt trigger and D flip flops to latch one of 4 leds. This way you could clearly see which of the fault conditions of the drive had operated prior to being reset by the controller. Our trade has been full of guys building great custom tools, often mechanical to get things done.
The 1092 IC panel was a true digital ETS based dispatcher. The Otis stuff is at heart still a zoning system. The IC panel was a better design in that you could easily pull a car out of group with the ribbon cable boards and they didn't wire 110vdc relay logic right beside a 5v pin. Otis, you could really do some damage if you got careless with a meter lead or logic probe. I think I got stuck doing every fire service overlay on the 1092 IC. I had to build custom boards for the phase 2 operation. Geez thank God that stuff is gone. It might scare half of these younger guys right out of the machine room. An 8ft tall cabinet with up to 48 circuit boards per car and another 2 to 3 dozen in the group section.
