Electronics > Projects, Designs, and Technical Stuff
Playable electronic modules - modules in action
HendriXML:
I finalized the soldering of 1 module.
First time using lead free solder.. (The toy is boxed, but better to be safe. Don't know whether the perfboard is lead free anyway. )
I had to take care not to heat the plated holes to much. Had to clean solder once and then the plastic sticker locally melted. Besides that it went well, but it is very time consuming for something that supposed to be cheap :P.
Only used 2 isolated wires. Most of the connections on the IC are made by creating a small wire loop at the end of an thin wire to keep the thicker wire and IC pin together and soldering those 3. Should make desoldering easier. But it is probably still a lot of work to replace the IC.
Maybe on the next one I will do the IC first, then the sticker and finally the pinheaders.
HendriXML:
The PCB is now mounted in a 3D printed box, it has inside 4 stands in the corners of 10mm: high enough for the dead bug not to get crushed.
Had ordered some of those hex screws (AliE), I think they look great. They're not really needed because I had to squeeze the PCB in, but now I know it stays in :-+.
For complete DIY and the low cost I'm happy with the result.
It is quite sturdy and relatively heavy.
HendriXML:
While testing the module I found the inputs to be very sensitive when not connected.
Can I leave them floated or is pulling them to ground with let’s say a 10k resistor “obligatory”?
And what would be the highest resistor that is still functional? I choose a 10k because then the current loss is still doable when a lot of inputs are in use.
Gyro:
Ah, that's something that one of us should have picked up on. :-[
Firstly, yes, floating inputs are bad on cmos logic. I think you could safely go up an order of magnitude to 100k on the resistors.
That brings me to...
1. Input protection - you may want to add protection diodes to each input for static protection. Maybe overkill, socketing the IC might be an easier solution.
2. There are no VCC and Gnd pins on the box (aside from the PSU headers, which I assume you intend to daisy-chain). You are very likely to want to tie one or more inputs high or low when experimenting. You probably want to provide 4 pins of each.
OM222O:
Yes, as Gyro mentioned, either use TTL logic instead of CMOS (more power draw for more gates if floating inputs are a bigger issue)
or tie them to ground with 100k (47k to be on the safe side) if random readings on floating inputs are a bigger issue. it comes down to how large the project is and how lazy you are. I would personally stick to TTL as it's unlikely for you to be using lets say 500 gates at a time? even ben eater (youtuber) made a full 8 bit breadboard computer using TTL series logic and the power draw wasn't too bad. that will also saves you cost of the resistors (although fairly cheap) as well as soldering them in one by one (my main point of laziness lol).
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