555 timer circuit to control 12v solenoid air valve (for intermittent bursts of air).

Quote:

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Originally Posted by A_Camera

...but 12V 6.5W is over 500mA, so if he is going to use the solenoid on the picture he needs a transistor, or a small relay in between the valve and the 555. The 555 is OK for small relays but not for solenoids.

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I did not mention a solenoid

Right, got this made now. It's flung together into an empty air-rifle pellet tin I had lying about, but it seems to work alright...

I eventually used this circuit.

...you can get essentially the same thing for half the price here - I assumed at the higher price that this was pre-soldered - it wasn't..! The two pots that control the interval/pulse are a bit sensitive, but otherwise it's a decent enough kit and very easy to put together. I didn't need the fly-back diode after all.

Thanks to Clive for suggesting the switch to over-ride the circuit and keep the air on continuously - useful and pretty much a necessity..!

Here's a vid of it in action:

https://youtu.be/N3M1x4GMAtw

And for fellow electronics dunces, here's a diagram of how it went together:

Attachment 21621

Wal.

Glad you have it fixed up and running Wal. Have you put a grommet around the red/black wires out of the tin ? to stop chaffing.

Hi Clive, I didn't have any grommets to hand, so I've hot glued (around the holes) all wires going in/out... stops 'em moving about.

Wal.