Flexible Test Board

I find myself fooling around making little adapters to prove out some code, messing with LEDs & resistors & such, wiring the same thing over & over. MrsCrossroads spent several hours yesterday adding LEDs & resistors to an Uno protoshield to support a test, which is working great, but I have to ask her to connect it up as needed as I have no idea what is wired to what, and there is no clean way to add labels with all the component legs in the way.

I figured why not come up with something a bit more stable (& Labelled!) for testing, with a boat load of typically used components (see attached):
Status LEDs (20 for Uno, 40 for Mega) with 1K current limit resistors for ~ 3mA current flow)
Buttons - not sure how many yet, probably 8, in an extended area from the ICSP header on Uno and outside of the 22-53 IO header on the Mega.
Rotary Encoder (right angle) & filter circuit
2 trim type Pots (screw driver adjustable)
2 shift registers driving 2 7-segment displays - maybe change to MAX7219 & 8 digits of Bubble display (lot more cost tho - ~$9.25 vs ~$3.75)
2 Servo connectors for offboard servos
2A Servo only power supply (rest of board is powered by the underlying Uno/Mega)

So I’ve got this board all placed up in Eagle, with just a couple things left I am working on/ waffling on:

Servo power supply - I have 7805/TO220 flat on the board for a place holder for now, going to change that to a chip/inductor switching power supply for a 2A supply to 2 servos.

2 pots - I have 2 single turn 5K pots there now. Was thinking to just use them as reference levels - but maybe instead leave the high side open so it could be used for offboard signal voltage divider? 10K value instead?

There are a lot of LEDs - 20 for Uno size board, 36 for a Mega. Replace a bank (or some quantity) of those with a 74HC4050 so up to six 3.3V level signals could go out? (with 3.3V from the underlying Uno/Mega).

Squeeze in a couple N-channel MOSFETs to sink current to drive relays or other high current load?

I am picturing I will personally populate it with male pins and just connect stuff with wirewrap wire, make it solid for testing, and easy to remove & rewire. Others might leave the holes blank and solder in wires instead for something more permanent/harder to change. I did that with a 1284 Bobuino2 recently, and regretted soldering in wires as soon as I started. Especially when I found 2 wires that I missed by 1 hole each in placement.

Any thoughts?
Will post a board layout pic shortly.


Ooh, this is coming nicely! 10 4.5mm buttons, 2 N-channel MOSFETs added. Even a little proto area on the mega sized board.
Just need to work out the Servo supply and will be all set!
Then trim it down for an Uno, and figure out what to do for a 1284 board.

I did something similar but much less grand on strip-board a while ago, and still have some room to add more.

I have an adafruit oled screen and a DS1307 with the SDA and SCL lines to headers so I can chain more; might add an eeprom or two.

Then a bunch of buttons and a 4-way dip switch; one side is to GND so must just remember the pullup on the input. Couple of LEDs; I went for ones with resistors built in for 5V use, save a bit of room. My supplier only had those in red, alas. Couple of trim-pots. A piezo buzzer.

Probably going to add a 555 and sockets for its resistors and caps.

I like the idea of some transistors on there.

I'll probably double-sided-tape a micro size breadboard on there two.

Hi, I like the idea, just one thing I would do. Most projects I see on the forum, when it comes to actual physical construction, try and use SMD and make the project as small as possible. For prototype reasons you should be; Making it as big as possible, Lots of spaces for decent size readable overlay. Room to push your finger to plug the wire in. Room to feel if anything is getting hot. Room to easily unsolder components when the smoke comes out, NO SMD components, any IC that can be plugged into an IC socket, should be plugged into an IC socket. In other words make it SERVICEABLE.

Tom.......I should know, I have to service the SMALL, SMD, and UNSERVICEABLE. The impossible takes just that bit longer, and the hourly rate escalates. :)

I too did something similar. I use relays and analog sensors.

I used an 8 pin header, 2 for power for my protected side of my ADC circuit and 2 (raw power) for the field side, to protect from shorts. 2 Analog pins in, 2 back to the Arduino.

The idea is that I can make up an op-amp board with the correct 8 pins and plug it in.

I can use either an op-amp to scale a single value, or compare 2 values.

since you can get a LOT of small boards from a 10-board order of 5cmx5cm boards, the daughter cards are pennies.

when not used for the op-amp, I can just jump the inputs direct to the analog ins.

I used a pro-mini to get access to the A6 and A7

as for the relays, I use tiny DIP relays, drive by a PN2222, with an LED to show value. first round I put the relays in, next round, I just used the LED's third round I used a TIP120 and external relays, still have the LEDs to show the values.

TomGeorge: Tom.......I should know, I have to service the SMALL, SMD, and UNSERVICEABLE. The impossible takes just that bit longer, and the hourly rate escalates. :)

signs in an old motorcycle shop. $50 an hour service rates $75 if you watch $100 if you help Helen Waite is our credit manager if you desire credit go to Helen Waite.