Looking for solid state relay to drive with Arduino

Hi Guys,

In order to compact down my project and remove the bulky traditional automotive relay I'm looking at switching to an SSR (solid state relay). I've been googling them and reading up and they sound very nice. I'd like a bi directional (current can flow either way) unit I can use in 12 volt automotive applications and handle around 30 maybe 40 amps and be turned on/off by my arduino.

I've been searching over mouser.com but the volume is over whelming and a lot cost close to $100 and some as little as $4.

Anyone ever used SSRs and have some suggestions as to a good universal part # I could start with? Would love to order up a few and start playing around. Just completely lost as to which one to order.

Thanks Malcolm

Most common SSRs are designed to work with AC voltages only. You sound like your application is high current DC voltage? Also your desire that current "must be able to flow in either direction" is not a common attribute of DC SSRs which pass current in only one direction. So you may have a hard search to find something that will actually work for your application. But maybe you have just not clearly stated your electrical requirements?

Lefty

retrolefty: Most common SSRs are designed to work with AC voltages only. You sound like your application is high current DC voltage? Also your desire that current "must be able to flow in either direction" is not a common attribute of DC SSRs which pass current in only one direction. So you may have a hard search to find something that will actually work for your application. But maybe you have just not clearly stated your electrical requirements?

Lefty

I did not realize SSRs are targeted at AC voltages only. I must have missed that part. Yes my plan is to use it with DC voltage in automotive applications which can at times demand fairly high currents. The reason I want current to be able to flow either way is for universal hookup. I was trying to avoid it been polarity sensitive. It just confuses end users installing such an item.

I opened up an electronic box I have at home (something I purchased) and found it was using one called a VN920 which was $3 on mouser so I ordered a couple of them to play with. From the data sheet it appears to be polarity sensitive too. Bi directional and as close a function as standard mechanical relays would be nice.

Bi directional and as close a function as standard mechanical relays would be nice.

Sometimes the best replacement for a mechanical relay is with another mechanical relay. :D

Good luck with your search.

Lefty

LOL yeah I'm starting to think that.

The reason I want current to be able to flow either way is for universal hookup. I was trying to avoid it been polarity sensitive. It just confuses end users installing such an item.

It would be unusual for a system to have a high-current switching device that is not always configured as a Low-Side Switch (The load is connected to +12V) or a High-Side-Switch (Load connected to Ground).

What is switched in your application?

terryking228: It would be unusual for a system to have a high-current switching device that is not always configured as a Low-Side Switch (The load is connected to +12V) or a High-Side-Switch (Load connected to Ground).

What is switched in your application?

I have a variety of projects I'm working on. Some interrupt the ignition system, another interrupts the fuel injectors, another project sends power to nitrous solenoids and so forth.

If I have to live with a SSR been polarity sensitive it's not the end of the world. I could work with that too. I just need to know a good common part I can purchase and start testing with. Like I said the electronic supplies such as mouser have so many of them I'm lost as to what I should pick.

I found this one on sparkfun https://www.sparkfun.com/products/10636 but noticed it does say it's for A/C voltages. I assume I'd have problems with DC.

Looks to me like I could just get a 95 cent MOSFET and use it as a relay or electrical switch right? I think it would be directional... that part is not clear. The MOSFET has a Drain and a Source but it's not clear if power only passes in one direction or not between the two.

https://www.sparkfun.com/products/10213

MalcolmV8: Looks to me like I could just get a 95 cent MOSFET and use it as a relay or electrical switch right? I think it would be directional... that part is not clear. The MOSFET has a Drain and a Source but it's not clear if power only passes in one direction or not between the two.

https://www.sparkfun.com/products/10213

Found I already had one of these MOSFETs in my parts pile so I played around with it tonight. Real easy to use actually. I wired it up to a power pack used for jumpstarting cars and then grabbed a radiator cooling fan which draws at least 20 amps. Had the arduino controlling it with the PWM output pin 9 and was able to speed up and slow down the fan or just turn it full on. Very cool. I'm impressed with how easy that was and how little heat was coming off the MOSFET itself. I don't think I'll even need a heat sink.

Using this MOSFET allows my projects to be so much more compact I think I will live with the directional polarity requirement for the space saving advantage. Not to mention from what I read online I should get many robust years of usage out of a MOSFET and have reduced failure rate compare to the traditional mechanical relays.