Powered relay corrupts display

[PanFrie]

So I'm working on a water flow device (set volume with a rotary encoder, press button, and water flows until volume is reached). Everything is working just fine, until I plug in the power for the solenoid. Once the solenoid switches, the display gets all corrupted. With the 12v power supply not plugged in, the display is fine.

Here is a wiring diagram of the project (minus a few resistors from the encoder, but I don't think those matter for the current problem). The 12v supply is also currently a 15v (I misread before chopping it up...). Testing for a couple minutes doesn't seem to be a problem for it, but I guess might maybe be part of the issue.



I'm really confused by this, given that the extra power in the system is entirely separate from the rest of it.

 

[Martaine2005]

Huh?

 

[Harald Kapp]

Several issues here. The most immediate ones:

• 12 V relay powered from 5 V and a port pin of the PP? Does the PP have the capability to supply enough current to the relay?
• No flyback diode across the relay coil? Or is this a relay module with integrated driver? If so, tell us what it is. An integrated driver may eliminate the need for an additional diode and also allow control by the PP's port pin.
• PP powered by 5 V on the 3.3 V pin? A sure way to destroy the PP.
• Where's the power supply? How is it connected to the circuit?
• CS on the display floating? Never leave inputs floating. Use at least pull-up or pull down resistors to fix the potential when you don't have an active control signal.
• What is the box labeled START? Probably a switch? If so, use a switch symbol so we know which pins the switch connects. I have no idea what A0...A3 means in this context.

The flow solenoid probably draws a lot of current and may thus cause electromagnetic interference. Try locating the solenoid as far away from the circuit as possible. Also add a flyback diode across the solenoid to suppress high voltage spikes when turning the solenoid off.

Sorry, but with an incomplete schematic you can't expect a lotta help from us.