LEDSnapper - Probably the most basic piece of test equipment you can make

A very useful tool indeed! And a good idea to put them on printed circuits. Thanks for making the Gerbers available.

I handmade something similar a couple of years ago.

Two banks of 10 LEDS, one red bank and one green bank. At the time I was playing around with logic chips and would use one bank to show input and one bank to show output.

What I mean is decade counters, multiplexers, inverters, etc..

My other favourite simple tool is the Seven Decade Resister Bank, of which, I have two. They are just great to simulate and calibrate voltage dividers.

@pugwash

 That looks a little more sophisticated and probably therefore, more useful!

Do both banks light up at the same time? I assume the female headers are the positive voltage input. It looks like the LEDs on either side are connected up with one connection to ground(?) and one to the header? I can't really tell from the photo.

BTW That's what I have been doing: playing around with CMOS logic chips. I really don't have a better method for viewing output logic levels other than LEDs. I suppose there is more sophisticated equipment available.

--Mario

@mariog

The LEDs are connected to a common ground.

Each LED has a dedicated female header. Depending on which way around it is used, headers 1, 3, 5... are green or red and 2, 4, 6... are red or green.

All the LEDs are attached to high-value resistors, green to 3.3KΩ and red to 470Ω. The reason for this is not to overload the IC or µcontroller with too many mA.

An example is the 74HC595 shift register which has 8 output pins, each capable of supplying 20mA but the combined total current should not exceed 80mA. That is, 10mA per output pin if all output pins are lit up.

I just kept increasing the resistance until the LEDs were still visible but not lighting up the ceiling, prior to soldering the final board.

Current consumption is worth keeping in mind when selecting the resistors, but I wouldn't use 220Ω myself.

@mariog Thanks so much. I just downloaded the Zip files. I do a lot of breadboarding with LEDs. One circuit currently on a breadboard has 16 LEDs, each with their own resistor. Yes, it can be tedious setting up this many LEDs. Thanks also for your efforts to make and promote this as an open source project. I'm disappointed with AAC and their rejection. I always thought of them as being more open minded.  

@mariog I just discovered some of your other projects, fun stuff. Thanks for the Shakespearian insult generator, and keep up the good work. You're not such a mewling swagbellied footlicker after all 😉