Using a solid-state relay to control a solenoid

[tt92]

I am using a 08M picaxe with a A210DN solid-state relay to control the shutter on A Pentax DSLR and a couple of Canon DSLRs. These cameras have co-ax sockets for remote controls so the relay merely closes a switch so that the camera's battery can operate the shutter. Which is another way of saying that the voltage and current through the relay is trivial.
I want to do something a bit more ambitious and operate a tiny solenoid. The available solenoids are 12Volts and are rated at 10Watts (max). I know these relays operate successfully at 6Volts and this is how I would run them. They would be activated for about one second at a time. Would the A210DN relay (also called HFS2) handle this kind of task? If not, would it vanish in a puff of smoke, or would it just not conduct enough current to activate the solenoid?
Thank you.

 

[KMoffett]

No.

The for a 12V/10W solenoid the coil resistance is 14 ohms. At 6v the coil current is 400mA.

http://pdf1.alldatasheet.com/datasheet-pdf/view/194417/ETC/HFS2/A210DN.html

The A210DN is rated at only 150mA output current. And has a maximum 10mS surge current of only 300mA. Also, the ON resistance is from 12.5 to 50 ohms, that would appear in series with your coil.

Maybe no smoke....but on work.

Depending on your circuit, a resistor and transistor might be all you need. Can you post it?

Ken

 

[centrex]

Why not just a transistor driver as per the Picaxe manuals, dont forget the back emf diode.

 

[Andrew Cowan]

I'd agree with centrex, and use something like a (NPN) BC639. Good for 1A.

A

 

[manie]

Andrew: Question....

Won't a PNP be easier ? With NPN you have the "open" collector scene where a resistor is used to feed the load. With PNP you can feed the +ve straight through minus the (slight) voltage drop ?

 

[Andrew Cowan]

Both work fine in my experience - I prefere NPN as it doesn't invert the logic - input high = output on.

A

 

[MartinM57]

Not very keen on those transistors with open circuit bases - a bit undefined what state the transistor will be in when the switches are open.

High side is simple if you are switching a 5volt Vcc with a PICAXE output, but if for example the load needs a +12v supply then your PICAXE output at either +5v or 0V is going to make no difference if simply connected to the base of the high side transistor - you then need another driver transistor between the PICAXE and the high side transistor...

 

[BeanieBots]

No manie, a PNP would COMPLICATE things as described by Martin.
Simple NPN of suitable current rating would be a good simple choice and the back emf diode is essential to protect the transistor from over-voltage.

 

[hippy]

Also 'open collector' NPN's and darlington's with output NPN's come in cheap(ish), readily available and reasonably compact packages for driving multiple switching lines. Maybe there are multiple PNP packages ( no need to prove there are ) but they are not as frequently seen if they do exist.

From my non electrical engineer perspective, NPN requires just two things; suitable current rating and how to connect the base to whatever drives them. PNP adds a whole load of complication.

For switching anything which doesn't matter if high-side or low-side switched I cannot really see any advantage PNP would have over NPN.

If nothing else, that the drive goes high to switch the load on is extremely useful, both 'logically' and practically - particularly as many PICAXE initialise drive lines low at turn on ( after initial floating ).

 

[Dippy]

Do you actually need a clunky relay?

You'd have to check the Vs with a multimeter first, but if the camera connection switch is just a simple switch-to-ground then wouldn't an NPN switch or N Channel MOSFET?
On something more complicated maybe one of the those bilateral FET optoisolators might work.
But as I say, you'd have to check the coax connection Vs wrt ground first before taking this route and maybe how tiny the current involved is too.

Hasn't all this been done before on this Forum?

 

[KMoffett]

Do you actually need a clunky relay?

....On something more complicated maybe one of the those bilateral FET optoisolators might work.

That's where we started in the first post.

Ken

 

[tt92]

Thanks. I will make up some circuits with the transistor. I sort of wistfully hoped that the bits I had already made with the SS Relay for the other application might just work.

 

[Dippy]

"That's where we started in the first post."
- absolutely.

But then posts 3 to 9 related to relays....
I merely got hold of the tiller

Anyway, potentially dead easy if you measure things.