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Topic: Solid State Relays (Read 1 time) previous topic - next topic

Hi Gang

I am wanting to experiment with Solid State Relays. I was thinking of purchasing the following;

http://www.jaycar.com.au/productView.asp?ID=SY4092

Am I able to run this direct from a digital output pin?

Kind Regards

WN


silasmoeckel

Well it's listed as:

Control voltage range:4 - 6VDC
Max. input current: 20mA

So any 5v arduino should have no problem running it.  Besides the opto isolation that that a SSR provides, that device is barely able to handle more current than the cheapest through hole transistor that cost pennies. Any reason you think you need a SSR for low voltage DC under 2 amps?

Grumpy_Mike

Most SSRs handle AC only, this one handles DC only. Yes you can use it but a more economical way is to use a logic level FET.

MichaelMeissner

I'm not the original poster, but I was about to ask a similar question.  I have a camera that I want to control its shutter release (three wires, ground, focus, and fire).  In this case, there is no common ground between the arduino and the camera.  The camera supplies its own power and does the focus or fire action when the appropriate wires are shorted so a circuit is made.

I first bought a Jim-pak opto-isolator (4N26JP) from a local electronics vendor and then a 5v input, 24v 1a output SPST relay from Radio Shack.  In both cases, I'm struggling to know which pins to connect on the Arduino side to ground and digital pin, and which pins to connect on the camera side for ground and selection to allow the circuit to be completed.  The opto-isolator has one dot on the top presumably for orientation.  On both of them I tried wiring it up as I thought the data sheets indicated, and then tried various combinations.  Unfortunately the electronics vendor hadn't used opto-isolators before, and the Radio Shack clerks were more up on cell phones than components.

So if you could point me to a FAQ for dummies that gives the exact wiring for these devices, it would be appreciated.

Hi Gang

Thanks for the responses. I am wanting to use the relay to switch from one video input to another. I suppose I was concerned that the digital output pin on the Arduino can produce up to 40mA which is greater than the Maximum Input Current of 20mA for the relay. Am I right in thinking this?

Regards

WN

Arrch

I suppose I was concerned that the digital output pin on the Arduino can produce up to 40mA which is greater than the Maximum Input Current of 20mA for the relay. Am I right in thinking this?


The Arduino won't supply 40mA if the load is only pulling 20mA.

Hi Arrch

Thanks for the reply. I apologise for basic electronic knowledge. So what you are saying is that the Maximum Input Current of the relay is really the current that the relay requires to work ie 20mA? The fact that the Arduino can produce up to 40mA is irrelevant as it will supply what the relay requires? It will not damage the relay?

In addition, I have read that I can directly connect the Solid State Relay (SSR) to the Arduino digital output pin?

Really appreciate your help.

Regards

WN

Arrch


Hi Arrch

Thanks for the reply. I apologise for basic electronic knowledge. So what you are saying is that the Maximum Input Current of the relay is really the current that the relay requires to work ie 20mA? The fact that the Arduino can produce up to 40mA is irrelevant as it will supply what the relay requires? It will not damage the relay?

In addition, I have read that I can directly connect the Solid State Relay (SSR) to the Arduino digital output pin?

Really appreciate your help.

Regards

WN

Yes. A load, such as the coil of the relay, "pulls" a certain amount of current. If the load pulled over 40mA, you risk damaging the Arduino, not the relay. The coils in the relay can also only accept a certain amount of current before it fails as well, but the current it "pulls" depends on the voltage applied across it.

You shouldn't have an issue connecting the relay straight to a digital pin if it only pulls a maximum of 20mA.

Hi Arrch

Much appreciated.

Kind Regards

WN

Hi Gang

Could someone suggest a suitable 5V SSR DPDT Relay that uses less than 40mA?

Regards

Jason

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