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doubt in solid state relay connection

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hansika

New Member
Hi all,
i am having a SPST solid state relay, the relay is having four pins
pin 3 : dc control +ve pin

pin 4 : dc control -ve pin

pin 1 : dc Load +ve pin

pin 2 : dc load -ve pin

i am using this relay to give 24V DC to load with 5V control voltage , what my doubt is to which pin i have to connect 24V supply and to which pin i have to connect load.
 

ericgibbs

Well-Known Member
Most Helpful Member
Hi all,
i am having a SPST solid state relay, the relay is having four pins
pin 3 : dc control +ve pin

pin 4 : dc control -ve pin

pin 1 : dc Load +ve pin

pin 2 : dc load -ve pin

i am using this relay to give 24V DC to load with 5V control voltage , what my doubt is to which pin i have to connect 24V supply and to which pin i have to connect load.
hi, It depends if you want the LOAD in the high side or low side of the SSR.

The DC Load +V will always go to the more positive connection and the DC Load -V to the most negative connection.

Example say you want to switch a 24V lamp, connect one side on the lamp to +24Vsupply and the other wire of lamp to DC Load +V.
The DC Load -V would go to the 0V of the 24V supply.

OK, or would you like a simple sketch.?
 

hansika

New Member
hi, what is the difference between high side switching or low side switching here i am giving 5V supply to control pins and i want to drive a load which is operate on 24V supply(load is 8W). my relay is crydom relay its part number is MPDCD3. it is helpful if you explain me with a simple schematic.
 

ericgibbs

Well-Known Member
Most Helpful Member
hi, what is the difference between high side switching or low side switching here i am giving 5V supply to control pins and i want to drive a load which is operate on 24V supply(load is 8W). my relay is crydom relay its part number is MPDCD3. it is helpful if you explain me with a simple schematic.
hi,
Look at this diagram.
 

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mramos1

Active Member
In Eric's drawing, the "+V cont" is +5volts (pin 3) and the unlabeled pin below it is the ground side of your 5V supply (pin 4). Load is of course what you are the supply the 24 volts too, make sure you get the polarity right.
 
Last edited:

crutschow

Well-Known Member
Most Helpful Member
hi, what is the difference between high side switching or low side switching...
It makes no difference to the load. It's just whether you want the load connected to common or to the supply voltage.
 
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