Connecting multiple input devices to 8 channel relay board

Question

I have an 8 channel relay board (here's a link to the actual product (http://smile.amazon.com/dp/B00KT0E1RY/ref=sr_ph?ie=UTF8&qid=1463753455&sr=1&keywords=smakn+8+channel).

I understand how to hook everything up so that the inputs control the relays correctly, however I have one concern on my inputs.

I realize that this board may be designed more for arduino projects, but I have three different input devices (Axis Door Controller a1001) that have two outputs each of 12v. When one of the six outputs applies 12v, the corresponding relay activates the controlled device (in this case, electric door strikes).

My question: I noticed that on the input side of the relay board, there is only one negative terminal and 8 signal terminals. My thought is that the positive of the each input will need to be attached to the a signal port and the negative would get attached to the common negative. Will this be a problem with having all of the inputs negatives attached together? I know enough to be dangerous, but don't want to have issues if 12v from one input device is somehow interfering with the other devices because the negatives are all connected? I thought that it could be a good idea to have one relay board per input device (a1001) in case this might be a problem.

Thank you!

Answer 1

No, there should be no problem when you tie the grounds together. That is the normal way to get multiple signals to interact, by providing a common ground reference.

I don't have the schematic for the relay boards, but 12V may be too high for the optocoupler setup. A series resistor for each input may be recommended.

Answer 2

Your relay board was made to respond to logic-level inputs (as from an Arduino or other microcontroller). However your three different input devices (Axis Door Controller a1001) are outputting 12V. It is not clear whether this 12V output from the door controller will directly drive the door strike. Presumably not if you think you need a relay in between.

That relay board is not suitable for what you need to do. You appear to need just some ordinary, "raw" 12V relays. Perhaps like this ....

http://www.amazon.com/PODOY-HH62P-L-JQX-13F-PTF08A-Socket/dp/B0087ZTEBG/ref=sr_1_12?ie=UTF8&qid=1463755177&sr=8-12&keywords=relay+socket

Just one example of hundreds of similar solutions.