How to trigger solenoid with very low current?

[Kjetil]

Hi, I would like to use a very low current (something like 5-20 milliamps) to trigger a 9V solenoid. Since this very low current cannot be used directly, I am guessing that I need something like a relay switch. For the record, I am a complete novice when it comes to these kind of things!

My question would then be, is this at all possible? If yes, what do I need in order to make it work?

 

[Alec_t]

Welcome to EP.
How much current does the solenoid draw when supplied with 9V?
Can you post a link to the solenoid spec?

 

[shrtrnd]

Can you supply the information Alec_t asked for? That would help.
In your situation, without knowing your application, you are on the right track considering using a relay to
control a required current to the solenoid. HOWEVER, the only thing a relay does, is apply some other
power supply value (the current you need to activate your solenoid). A relay by itself doesn't supply it's
own driving current to the solenoid. Just wanted to point that out in case you don't know it.
Can you tell us more about your application? We can probably offer good advice if we have that.

 

[Kjetil]

Thanks for your replies!

As far as I understand the solenoid will draw something like 0.5 amps. Here is a link to the basic specs:

http://vi.raptor.ebaydesc.com/ws/eB...244&category=181878&pm=1&ds=0&t=1485290605105

Yes I understand that the relay will not provide a current by itself, but that is a fair question considering my level of knowledge

Basically, what I want to do is to build a kind of touch-sensitive sensor that should trigger the solenoid. My plan was to use thin parallell metall wires (that does not touch each other), spaced a millimeter or so apart, hooked up to a 9v battery. Then relying on a hand/finger to close the circuit. This weak current would then activate the relay switch, triggering a higher current to the solenoid.

Not sure if this makes sense at all..

Once again, thanks for your help. Its much appreciated.

 

[BobK]

You are expecting 5 to 20 mA through the skin? Think again. 10 mA would be a painful shock.

But don't worry too much, with 9V you would be lucky to get 10 μA, which is nowhere near enoufh to trigger a relay.

You need a touch sensitve switch circuit to do what you are trying to do.

Bob

 

[Kjetil]

Thanks for the tip!

 

[Kjetil]

Just before I order, would this touch sensitive trigger switch do the trick?

https://vetco.net/products/touch-sensitive-switch-module-arduino?taxon_id=2646

If yes, would it be possible to hook up the "touch sensitive" part to a couple of very thin metall wires of say 1.5 metres and still retain the effect?

 

[Alec_t]

Difficult to say from the write-up for that switch. If it's too sensitive you may find that 1.5 metres of wire makes a good enough antenna to pick up sufficient interference to give false triggers.

 

[Kjetil]

Hm..good point. However it says that it should be possible to adjust the sensitivity. Think I'll buy one and give it a go. Not a huge investment in any case. Thanks for the reply!