Servo switch and wiring layout questions.


Im a bit of a noob when it comes to electronics but slowly learning. Im making a replica portal gun and finally about to tackle the guts of it.

I was wondering if someone could have a look to the wiring schematic i drew up and tell me if there is something glaringly wrong before i go and fry yet another board.

Give me one sec if the attachment isnt there.
Thank you in advance for any help anyone can give.

By the name, yo already know that is NOT a schematic. It is really to difficult to try to follow all the colored lines to try to figure out what is connected to what, and then there are the things that cannot be identified. Just do the schematic!


All your switches are wired wrong. The digital inputs will be disconnected and floating when the switches are off. You need to add pull down resistors or do the sensible thing and ground them instead of using +5V, and use INPUT_PULLUP in pinMode to enable the internal pullup resistors.

Also, driving NeoPixels from a PCA9685??? Have you tried this?

What’s the voltage requirements for the PCA9685? Can you give it 7.6V?

What’s the voltage requirements for the PCA9685? Can you give it 7.6V?

Good catch, but I think that's the PWM power input, and should be okay. The bad part would be driving NeoPixels on 7.6V... :wink:

You want to bet smoke on it?

Check the back of the board in the pictures.

I could be wrong but I don’t think you are supposed to run Dc motors directly from an arduino. You would need the output pin connected to the base of a transitor and drive it with the transistor.


so how about linking the arduino and the pc9685 in series. that would give it about 3.7v? unless anyone can recommend a dc voltage step down board.

As for my switches Arrg this is why i asked. let me have a look at those internal pull up resistors. This is the bit thats new to me

I am aware of the limited power of the arduino and did wonder if i was overloading the board but since its small load stuff i thought i could get under the bar. If its a concern ill try add transistors too.

thanks for the replies

Can you post a picture of the portal gun?

That's it so far. like i say the internals arn't finalised and i'm going to be properly weathering it and paint it when its finished. it will also be available for download and print as a kit so you could build one too.

Nothing I see gives me much faith it will work yet

like i've said i'm not brilliant at electronics. I'm teaching myself from the ground up so im sorry if im not giving you much confidence. Im struggling to upload pictures of my work due to the 2mb limit on pics but ill keep trying.

Thanks for the help so far.

Just get your project working before offering it up as a kit. Walk first. You need to listen to some of the comments offered by aarg and do some research and testing, you have ways to go. I would check back with specific questions once you get it going. I see plenty of issues with your circuit but you should do some footwork first. Take each part and research how to do it. Otherwise just ask someone to correct all the issues for you.

ive actually have been researching pull down resistors right now. That was a very useful piece of information. I do understand i have a long way to go. the end goal is to give as a kit and i understand im nowhere near it. I knew that 5 years go when i started and i know it now. you say you see plenty of issues, well rather than putting me down make a list so i can learn. Im only trying to ask the question because i don’t know and im not afraid to admit that. you say get it working and it its 100% mechanically. all i need to do is plug the right components in the places and it will work which is why i’m here again. anyway ive made some amendments based off the suggestions here.

Thanks for all thoes who commented.

Research how to run motors with an Arduino. There will be an amazing amount of information out there. That’s the next glaring issue.

well thank you. I found a nice tutorial on using mosfets and a diode to do what i need.


so Ive done a revision. I’ve removed the detracting colours and researched pull down resistors and powering motors via arduino (not recommended). Any thoughts on this diagram?

Thanks for the pointers.

those diode would short to ground... think about anode and cathode and direction of current flow.

Is that the only thing though? easy fix.

that's about as far as I got... sorry busy with my other projects... I do this to help so it's up to you to get it complete and right.