Hi all,

I'm trying to build a battery-powered, button-actuated solenoid controller circuit.

Here's the circuit schematic:

This whole circuit works fine on a big breadboard. But, when I miniaturize it onto a 2" x 2" solderable breadboard, it breaks. The relay chatters endlessly. When I hold the button, it continuously opens/closes at a high frequency instead of staying open.

I'm using this DC buck-boost converter from Amazon. And this relay module. As well as a momentary SPST button to control the triggering.

(Interestingly, the miniaturized circuit works fine with a 12V 1A solenoid but only chatters with a 12V 2A solenoid.)

I'm pretty certain I have some stability issues and need decoupling capacitors in a place(s). (I'm certainly not using any best practices here. The first version of the miniaturized circuit used zero capacitors.)

How I can fix the chatter?

My plan was to rebuild the circuit and:

• establish a common ground with the source batteries + post-converter ground
• add a 470uF electrolytic decoupling capacitor across the post-converter Vout + and -
  

I have to rebuild the circuit on this Adafruit breadboard, because of size constraints in the project container.

I was planning to put basically everything on the +/- buses with the decoupling capacitor across that. I'm not sure if I should breakout the post-relay solenoid wires and, before rejoining with the bus, insert a decoupling capacitor there too?

ChatGPT suggested a simple resistor/capacitor debouncer on the SPST button but I have a hunch that it's not bouncing (it hasn't shown any bouncing behavior when I've used it elsewhere).

Appreciate any feedback here!

 

Welcome to AAC!

Did you change any components on the soldered version?

 

Nope soldered version is the same circuit. The soldered circuit actually works for a 12V 1A solenoid, but chatters for a 12V 2A solenoid only.

 

your links are the same, no link to relay module.
if the 2A load causes chatter, clearly circuit cannot handle 2A load.

 

(Interestingly, the miniaturized circuit works fine with a 12V 1A solenoid but only chatters with a 12V 2A solenoid.)

Leads me to wonder if at 2 amps you aren't pushing the envelop with the buck converter since a 1.0 amp load works fine and a 2.0 amp load the relay chatters. Next, most 2.0 amp rated inexpensive buck converters will not deliver a full 2.0 amps.

Ron

 

No doubt it is insufficient supply current.

Instead of the DC-DC converter, hook it up to a 12V battery, or a PSU that can deliver more than 2 amps. That will confirm it.

 

Welp. Indeed, it was insufficient supply current.

I was using 16x AA batteries that seem to have died.

Hooked it up to a car battery and it worked like a charm.

Thanks everyone!

 

Why were you using 16 AA cells to give 24V and a DC-DC converter when you could have used 8 AA cells to give 12V?
If battery life is an issue, most solenoids will stay held in even if the drive voltage is reduced by half (which reduces the power by three quarters)

 

Why were you using 16 AA cells to give 24V....

Maybe not. I read it as a bunch of cells in series-parallel with the converter to cover battery droop. Who knows....

 

Voltage drop caused by inadequate current capability can certainly cause that sort of symptom.