Opinion on Solid State Relay

I’m going to make a machine PCb to get rid of the rat nest I currently have. (It only works part time right now). It’s on my large lawn.mower-sprayer- junk hauler. I only need 3 relays. I want to use Solid State Relays because my CMPS is in the same glovebox. There’s only so much room on a mower.

I’m looking at using a Digikey CLA325-ND SSR. Can any of you much smarter people than me see why these won’t work? The folks at Digikey thought they would.

I’ll run 3 solenoids . The ones I’m hoping will work only pull 400 ma. If I need to go heavier then 1.3 amps.


the 325 seems rated at 2A. Nice relay that only needs 10 mA and is opto isolated.

What are you pulling for current on each load? If less then 2A, i’d say good choice. use about 390 ohm resistor for 10 mA input current.

I’ve written a new machine module code and AOG config page allowing to to program any function to any pin.

This component works with mosfet logic, wouldn’t it be more convenient to use mosfet directly? The currents are also very high.

Looks like the relay would work just fine, 17/12 = 1.42 amp. Be sure to add a flyback diode.

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@BrianTee_Admin, The solenoid I’m hoping will work is this one (light weight) - 12V 320 mA. If that doesn’t work I’ll use one like @whiterose shows which will draw 1.3 amps.

I actually have a mosfet and opto-isolator coming. I’m going for the smallest footprint possible cause of space limitations so I’m going to get this relay coming.

I saw this, Is it live in the newest release?

I need to learn more about the hardware side of this, what is a good resource for learning? I’m old and the newest electronics stuff in my early years was electricity it’s self. :grinning:

Thanks for the affirmation that I’m on the right track!!

Yes that could work, but the nice thing about the solid-state relay is that it isolates the arduino digital output pin through an optocoupler so if something goes wrong with the solenoid it has less chance of taking the microcontroller with it.


You are right, I suggested it because the current of the mosfet is higher, I use optocoupler in my own setups, I also use a fast diode parallel to the solenoid valve.

I’ve got some 1N4007-T (DIODE GEN PURP 1KV 1A DO41) and some 1N4004RLG (DIODE GEN PURP 400V 1A DO41). Will either of these work?

According to Google the rating of the diode should exceed the working amperage of the coil, which will be the same amount of current dumped when the coil is disconnected. The coil pictured above was 1.42 amps. You need a diode capable of passing that current. Both of the diodes you linked to can handle 1 amp. So two diodes in parallel should be plenty.

Thanks @torriem, I’ve ordered some 2 amps. Good trick using google to get an answer, I gotta remember that one!! :grinning:

When voltage is applied to a coil or relay, a reverse EMF (electromagnetic force) occurs. This is Lenz’s law, we use a diode to dampen this EMF, if we do not use this diode, a voltage of up to 700 volts will occur at the relay coil ends, which can break our electronic circuit. If our relay or solenoid valve opens and closes slowly, the 1N4007 diode may be sufficient, but if it is used as PWM at high frequencies, it is recommended to use a fast diode.

@whiterose, Learning more all the time!! I didn’t know about the fast diode. I was thinking about at least playing with PWM. The one I have selected at this point says “Ultrafast 20 Nanosecond Recovery Times” . It’s a MUR210G.

Since I know nothing, is this a fast one or is the “Ultrafast” just sales hype?


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I’m not very professional, but I always use UF-4007, mur210 seems to have low voltage. I use this when I use a PWM nozzle (20 Hz.)

Haha! I’m definitely not that smart so I figure I have to give credit where credit is due.

@whiterose I was only able to find a 1A UF4007 at Digikey. I did find this UF5408-E3/54 which I think is very close to the UF4007 but with 3 amps. What do you think?

I looked up the valve you show but I can’t find any pricing or where to but, just send for info. Is this made for PWM? What did it cost you, if you don’t mind me asking.

The article you referenced was helpful, thanks

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Also consider that 1A is long term ampere, short term is 30 A, so I believe 1A is will last :slight_smile:

@Larsvest Another thing I learned!! Thanks

Hi Ray, sorry for my delayed message, unfortunately the valve in the picture is not PWM but only a solenoid valve that works with 70 l/min and 40 Bar for on-off, the price in my country is around 40 Euros. You can find it in Arag, Tecomec, or sirfran.

But the product that makes the switch on and off at the bottom is 20 Hz. I used it until the end of the day, it is attached to the side of the existing nozzle, I used it for its intended purpose, but it works because PWM nozzles are expensive. Video is my own shot.(slow motion 25 Hz.)

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Can you get a varying duty cycle out of it, though? Most PWM systems pulse at a constant rate, but vary the on time to off time. Also the link you posted doesn’t work for me to the tecomec site. I’m interested to see more about it. What is the current flow at full on? Commercial PWM systems run at about 6 watts per nozzle. Quite a drain on the alternator! My AC fan slows ever so slightly when I turn on the booms! I figure it draws about 40 amps total for 120 feet.

Unfortunately, there is not much explanation on the site, yes, it is possible to use the duty cycle, we have set the flow with duty, I am still working on it, I am planning to keep the pressure constant and change the duty cycle according to the speed of the vehicle and check the ratio, it is necessary to control the flow between the left end and the right end when the vehicle turns, This apparatus is attached to the existing nozzle. (Installed instead of drip breaker section) Arag uses booster for seletron.

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