how do you connect Solid State Relay? for automatic T control?

Question

I have SSR with
1-2 output 120VAC 25 A
3-4 input 3-32VDC

I have temperature controller output at 5VDC connected to 3(+) and 4(-), and when temperature is more than 30'C it will turn down the 5VDC to 0. how do I connect a fan blower to turn on when the temperature is more than 30'C? I connect the fan through 1-2 without any response. please help

Answer 1

Actually, if you have everything connected correctly, your fan should now run when the temperature is BELOW 30 degrees. Correctly means, one fan end to Neutral 110VAC, the other end to pin 1 of the SSR, and pin 2 of the SSR to Live 110VAC.
If it doesn't then either your SSR is fried or out of specification, meaning, it doesn't trigger on 5VDC.
The other possibility is that your 5 Volt output from the temperature sensor is "too soft", i.e. doesn't supply enough current for the SSR input, causing the 5Volt to fold back (drop below 3 Volt).
In any case, you need to invert the signal from the temperature controller, so you get a "high" signal when the temperature exceeds 30 degr. and not a "low" one.
A transistor in emitter stage would do the trick: Your 5VDC through a 10kOhm (or so) resistor to the Base, the Emitter to 0VDC, the collector through a 560Ohm (or so) to "Plus". As "Plus" I would choose a separate DC supply which is higher than 5Volt, say 12 Volt (and both "Minus-es" tied together). Then you are not so close to the lower limit of the SSR's trigger voltage.

Answer 2

Solid State Relay Temperature Controller

Answer 3

Sound like you have the wiring correctly connected on the 5Vdc side. The SSR output shout be wired in series with the fan. 125VAC HOT to (1) , SSR Hot output (2) to the Fan, Return from the fan to Neutral.

You need to know what the 5VDC output signal from the controller is. (Either PWM or ON/OFF ) PWM gives power control and acts like a light dimmer, directly starting and stopping a motor with this method PWM is not recommended as the power is gradually applied.

So it sounds like you need to configure your controller.

There should be a programming mode which is entered by holding down a key for a few seconds. You should have a manual as there will be a cople dozen settings that can be made.

One of these settings is DIRECTION or HEATING/COOLING mode. Cooling mode turns the fan on above the set point while Heating mode does the opposite.

You will need to configure the proper thermocouple type and most likely calibrate it.

Also the controller may have an alarm mode, there may be several different alarm modes some of which will kill the output if the unit goes into alarm. So a misconfigured controller which is prematurely going into alarm could be killing the output


You will need to spend some quality time with the manual and download a copy from the internet if you don't have one so you can properly config the controller...

Answer 4

Solid state relays are normally intended for switching 120/240V AC loads like heaters. They are intended to switch around the zero crossing of the AC cycles. Usually the switching element is a triac device. This is great for heaters or lamps, not so great where inductance is present, like an AC motor. When switching a DC motor, it probably does not work at all, very likely staying "ON", but the truth is these guys were rude and uncouth, and should encourage others instead of trying to show how smart they are (or are not). The description I gave is how they are generally, but not all of them are this way I suspect. The solution for switching a DC motor usually involves transistors, sometimes in a configuration that allows reversing, and generally the arrangement is so the transistors can be switched rapidly to vary the speed (pulse width modulation PWM). Look up H bridge for details. The link shows the basic idea, where there are 4 controlling signals from a logic source using the same supply voltages in this example. Each transistor is either on or off according to its control signal. Current can be passed through the motor in either direction. The second link shows a simple switch where the motor cannot be reversed (Figure 9).