Can I use this Relay Board with the Pi ?
Because This board doesn't have Opto-Coupler..can i drive it from 3.3v...will It Cause any Issue for Pi
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I was actually looking at using a relay DPDT or H bridge similar to that but if anything, I realised you were possibly using a solenoid like I am, I went to a few electrical engineers and they recommened that I use a irf640 for a 5v 1a (low voltage application) and if I needed to apply more power with less power consumption use a irfz44 (for high power applications) in saying that (read the documentation for a irf640p) the advantage is that as long as you are using a digital output that supplies more than 4v 750ma (check documentation because I'm going off the top of my head) the connection internally will complete the circuit and allow the solenoid to run.
But I must stress that dont use the 5v supply off the board because the spiking current pull of the solenoid might have a high chance of destroying your board, may I suggest also using an external power plug pack with an inline fuse (roughly rated at 1A-1.5A)
Otherwise make sure you use a 100ohm to 220 ohm in series with the base of the component because all it needs is a current limiter to protect the irf640.
Sorry I just realised you were using a SPDT on the output circuit, either way this all still applies as this can work for most circuits.
Hope that helped mate.
From the picture of the board, the schematics and the components values given it seems highly likely that the board could be operated safely from a RPi GPIO pin.
A flyback diode is included to prevent the transistor from dying. The current from the IO pin to the base of the transistor should be less than 1.5mA at 3.3V. So assuming the maximum power rating of all IO pins is not exceeded this should be working fine (note: the total current all GPIO pins should be less than 50mA). V+ has to be 5V to drive the relays. The GNDs of the RPi and the relay board have to be connected of course.
I will probably use a buffer or an array of optocoupler in the middle before connecting something to the Rpi, obviously the cost will increase but at least you save your board everytime you connect any type of defeat hardware, specially with 120/230Vac.
Speaking of optocouplers, they are tested for 2-3-5-7kV isolation.