Part of my Arduino project uses 12 V DC linear actuator (0.5A) controlled by two 5V relays. I would like to connect flyback diode to the actuator but not sure how to do it because to extend/retract the actuator the polarity is reversed.
With other device (like solenoid) it seems straight forward as it is in parallel and in reverse direction to + voltage but here I simply don't know.
Why would you want to do that?
Perhaps more usefully you could connect a capacitor across the 12V suppy to prevent a sudden load causing problems. Does the 12V supply feed anything else?
The diodes are unnecessary and, as you have already determined, unworkable. Your relays provide isolation between your motor and the rest of the circuit. If you want to reduce electrical interference from the motor solder a 0.1microfarad capacitor between the motor terminals and one from each motor terminal and the metal body of the motor.
When relay opens after retracting the actuator (sometimes after extending as well) it causes LCD 16x2 to display random characters. This was happening with 2 solenoids I have in other part of the project and when I've added flyback diodes for these solenoids problem stopped. So I was hoping this would solve my problem.
Yes, PS feeds as well two solenoids 12v, 1A (connected to another 2 relays)
I found one topic online suggesting that 2 zener diodes connected back to back to each other and parallel to linear actuator should work but couldn't find any details online about it.
Your two relays are in effect an "H-bridge" driver. This would normally be made using MOSFETs but you are using relays instead. There is a standard way to add commutating diodes to H-bridge drivers. There is a schematic shown here:
It's easier to see where to connect the diodes if you draw the relays differently, like this.
A simple way is to use a bridge rectifier (which contains the four diodes)
Positive and negative of the bridge rectifier connect to positive and negative of the supply,
and the two AC terminals to the two motor pins.
Leo..
Hi,
Are you using the 12V supply to also power the controller?
Can you please post a copy of your circuit, a picture of a hand drawn circuit in jpg, png?
Hand drawn and photographed is perfectly acceptable.
Please include ALL hardware, power supplies, component names and pin labels.
Can you please post some images of your project?
So we can see your component layout.
Have you got the actuator wiring and the power supply wiring away from the controller board and associated wiring?
I am sorry.
I was trying to keep everything as simple as possible that's why I've pasted only the schematic of the actuator circuit (I hope everybody can see it) and I am just looking to add flyback diode to it at the moment.
As suggested I will try to add TVS bidirectional diode and hope this will help as flyback diodes helped me with other devices.
If this will not resolve my problem I will create new post with full schematic, pictures of the actual project and more details.
Thank you very much for your time, patience and all replies.
As has already been explained that isnt the right solution to your problem.
We call that "superstitious learning". If the problem is due to the sudden load affecting the supply you need to look at other solutions, a flyback diode or suppressor caps or TVS wont fix it.
However, the rest of your circuit can be influenced by the actuator circuit.
A full circuit diagram and some images of your project would help to properly diagnose your problem.
Get out your pen(cil) and paper and reverse engineer your project.
You need a good schematic to help in future problem trouble shooting.
Hand drawn and photographed is perfectly acceptable.
Please include ALL hardware, power supplies, component names and pin labels.