I am controlling 32 solenoid valves using 32 separate relays, and I have 4 basic 8-relay boards wired into my arduino to control them. I was recently reminded that I should be using clamping or "flyback" diodes to keep the voltage spike from arcing inside the relay on the 12vdc (solenoid) side of the relay. I have this set up nicely with my breadboard and jumper wires, but soon I will be transitioning into a full prototype with solder, screw terminal connections, and other more reliable connections. Each relay output will be directly wired into a solenoid, with a clamping diode, and all 32 will be sharing a power supply. Only one relay/solenoid will ever be active at one time.
So my question.. Do you guys have any suggestions on how to wire in 32 diodes to 32 relays and solenoids without creating a mess? I saw something called a "Clamp Diode Array Module Board" which looks nice and neat and has 16 diodes on it, so I would only need 2 (maybe 4 depending on how it works I have no idea). Would that work for my project?
here is an example of what I am talking about, and I will attach the provided wiring diagram in this link as an image below.
Also, is there a way for multiple solenoids to share the same diode or is that just madness?
I hope the wiring diagram is okay, I threw it together in PowerPoint for this post
EDIT: The diagram looks good but note that the
top bottom row of diodes do all the work of clamping the solenoid coils when the relays turn off (open). The bottom top row of diodes don't do much.
I should also mention, I do not know how to connect the clamp diode array module board to my components in order for it to work as in my full diagram. Help with that would also be much appreciated
I see you have a common ground and are switching +12V to each solenoid coil, so actually it will be the bottom row of diodes that are useful, not the top row.
Screw terminal V- connects to GND.
Screw terminal 5 goes to a Relay5 NO terminal
Screw terminal 6 goes to a Relay6 NO terminal
Screw terminal 7 goes to a Relay7 NO terminal
Screw terminal 8 goes to a Relay8 NO terminal
Only 5 connections (per diode array board) ... that's it.
I presume the bottom diagram shows if you connected diodes separately ... a cheaper solution (but more work).
If you are using soemthing like this
it looks as if the relays already have snubber diodes and optoisolators on the inputs.
"12V 8-Channel Relay interface board, and each one needs 50-60mA Driver Current. "
so you may (ie WILL) need an interface board if you are driving 32 * 50mA from an arduinio.
I saw something called a "Clamp Diode Array Module Board" which looks nice and neat and has 16 diodes on it, so I would only need 2 (maybe 4 depending on how it works I have no idea). Would that work for my project?
I suppose it would but only eight diodes are doing anything useful so you clearly would
need four of them. This diode array is more appropriate for a reversible motor system.
The screw terminals do make it very convenient to wire in however as you have two terminals to each diode connection so one wire from the relay board, one to the solenoid.
That board looks like a waste of 8 diodes, since you only ever need one polarity in an array like that.
Is there a reason you can’t just use 4 ULN2803 chips for all the driving and diodes?
Is there a reason you can't just use 4 ULN2803 chips for all the driving and diodes?
Presumably the solenoids require much more current.
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