[SOLVED] What the best driver for controlling SSRs using a 5v uC

[Xenobius]

Hi,

I am currently building a small reflow oven for the fun of it and have settled on using 2 Solid State Relays (mounted on heatsinks and all that) and controlling them using an arduino. My question is, with the parts that I have available, what do you recommend I use to switch on/off the relays? One certain thing is that I cannot/shouldn't directly connect the arduino to both relays simply because they draw a maximum of 25mA and the Arduino is 20mA max.

SSR specs:

Load Voltage	24-380VAC
Control Voltage	3-32VDC
Control Current	3-25mA
On Voltage	<1.5VAC
ON/Off Time	<10mS

Parts available:

Mosfet	78-SQ3427EEV	https://eu.mouser.com/datasheet/2/427/sq3427ee-101865.pdf
NPN Transistor	BCX5416E6327	https://eu.mouser.com/datasheet/2/196/bcx54_bcx55_bcx56-59453.pdf
PNP Transistor	PMBT3906	https://assets.nexperia.com/documents/data-sheet/PMBT3906.pdf

 

[betwixt]

Two transistors, NPN is probably easiest with the SSR in the collector.

Brian.

 

[FvM]

Most solid state relays with low voltage DC control input have opto coupler with series resistor as input circuit.

Did you check the input current with 5V control voltage? I would expect below 10 mA. If so, it can be well driven by µP pin without driver transistor.

 

[Xenobius]

Most solid state relays with low voltage DC control input have opto coupler with series resistor as input circuit.

Did you check the input current with 5V control voltage? I would expect below 10 mA. If so, it can be well driven by µP pin without driver transistor.

No the relays are still on their way but im going with datasheets while I design the circuit. You may be right however I think I will still feel better off with 2 transistors also considering its a one time project and I have hundreds of them

 

[Xenobius]

Hi again, so is this what you meant when you said SSR in Collector?
The 'CONN-SIL2' will be the 2 inputs of the SSR. Thanks

 

[betwixt]

That is correct. Double check the SSR has an internal series resistor to limit the current as described by FvM. Almost all of them do.

Brian.