Let's Make Robots!

My first PCB

Hi guys,

I started on some unfinished projects again but I could use some advice. I'm trying to build a board for the mini reef that can switch 6 devices (solenoid valves) at 12v DC with the PIC/Prop controller. I'm using diptrace for this as this seems to be the favorite choice. So far I love it.

I came up with the below but I'm running into some problems with the traces. Maybe someone can point out the right direction as I think that it must be possible to cross over a line (with some electonic component maybe)? The red circles are the problem areas.


In addition, I'm probably making mistakes since this is my one of my first pcb drawings: Please tell me if I got something wrong. It basically does (or is supposed to do) this: 12v DC goes in, 5v DC goes in, the PIC controls the relay coil at 5v, 6 channels, 6 times 12v switchable (on/off) output. Each relay can handle 1 amp, the fuse is 6 amps. I used oddbot's "regulated power supply" with the 470uF and the 0.10uF capacitors to prevent peaks on any channel. Since it will go on and off frequently i just guessed this was a good plan. For switching the coils I used the 2N2222A transistor with the 1N4148 diode schematic. This kind of sucks as I wanted to run it of 12v all together (and just use the PIC to deliver the 5 volts, but thats a bad idea I read down here). Dropping the voltage and turning the board into a watercooker doesn't attract me so I'm going for an extra powersource (prob some rechargeable cells and maybe a solarcell to keep it full). Maybe I could even use the 12V battery to charge the 5v (4.8v) ones. The latter seems more efficient then using a voltage regulator.


Thanks for the advice!

All the best,




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Is the number correct?
L7905 is a negative 5V regulator, you should be using a L7805 that is a +5V regulator.

That was it! I had them both on my desk and probably took the wrong one. Swapped them over and things came to life without overheating. It's also able to control 1x 12v relay. It is suposed to be a temperature controled water heater so the bird bath doesn't freezes. I'll post that a little later as it uses a picaxe also.



Chris, does it matter on which side the traces are really? I can turn it over and stick the components in the other in way can't I? Is it just astethics (not having a nice print on the right side) or am I missing something else? Maybe I'll see it tomorrow, I'm sick at home and can't focus very well I'm affraid...... Being sick at home reminds me of christmas somehow, you know, I'm dreaming of a white christmas. And if I run out of white I'll grab a bottle of red ;)

OB, man I just googled it, please let me state that I also have to google which polarity the flat side of a led has. ;) Hence, I'm trying. But when this is not a job (i'm an MS engineer; I know Nothing, Google is my Lord and Service Packs are the Solution to All Problems) the symbolism is pretty odd. But yes, you are right, I'm lazy also. Thank you for motivating me. :) Give me a few days, I think it's doable. However, I still am tempted to think that the eventual PCB layout remains equally important if not more. I salute you Sir and whish you a good Nap!

I just noticed the problem. Bummer :) Damn relay's.

I tried the diptrace schematics but it's giving me a headache. I can't find no pins/headers so I used a bat instead. Now when the thing compiles it into a pcb I get a really strange layout. It's trowing my control LED's all over the board with no real logic.

When in the PCB mode I can select a lot more things, in schematic mode they seem missing or have a different name. Phew, hard man.


You have my sympathy DutchBot, but please don’t give up.
I do agree that the hardest part in DipTrace is to find the actual parts and the organization of the components suck. That is why I made my own library and copied all the parts that I have and need in to that library.



What I feel is missing is some power and ground rails. You will find them under Ports_Sch
So if you put in several +5V ports and ground ports all will be connected. You can verify this by holding your cursor over a line and the net will be highlighted.

These seems not to be connected to anything but there probably should be a power and ground net connected to it.

Thanks Geir, as always very helpfull tips. I placed the 5v and the 12v supplies on the board now, the red area where you noticed no power should be ok I think. It's getting its 12v power from the relay (the large vertical strip in the middle supplies that. I added some 12v - poles to the top (to which the solenoid will be connected) but I can't find something like a 2 hole connector in diptrace (marked with red). 

No connector for 12v (relay powered)

Here is a close up of one of the circuits (6 of them do the same)


Close up of relay circuit

R1, R3 and R4 (1k) etc will connect to the signal wire of the Pic. It should then be able to switch the relay without burning the pin. C6 and C7 are the caps that oddbot used in his regulated power supply (470uF and 0,10uF). The there is an indicator led with a 470 resistor that goes on when the relay gives power. The U3.1 is the solenoid part of the relay, the U3.2 is the part where the power goes in and out.