Solid state relays

[thryll]

I am using a temperature controller in order to control some heating tapes. The output of the temp control is 5 volts when I hooked it up to the input of a SSR 3-32V the output of thetemp control drops to @ 1V if I leave the volt meter accross the input the voltage rises to an acceptable level @ 3.8 as soon as it shuts off the cycle I lose the voltage again. Then when it is retriggered I still do not have enough DC V (@ 1V again).

I seem to vaigly remember having this problem in school we would use a diode across the DC input I am fairly sure but I do not remember the biasing or the type of diode.

I felt this would be a cheaper solution than just buying a new temp controller thanks

 

[buzzp]

More clarification is required.
Based on the way I understand your statements, is it possible the gate current for the SCR is higher than the controller can source? These are generally only 'logic' type outputs not capable of sourcing much current (25mA or less). This would be consistent with your statements because the voltage supply will 'brown' out if too much current is being pulled.

 

[jraef]

Actually it sounds as though you have a 4-20ma output on your temp controller and a 0-5VDC input on the SSR. If so, you are in trouble. Check the controller and see if the output signal is configurable and check the SSR to see what kind of signal it needs. Quando Omni Flunkus Moritati

 

[dydt]

hi..
is there a dry contact or voltage free contact on this temperature controller? this contact open and closes on your preset temperature..you can then use this contact to drive an SSR using the available voltage you have..DC or AC..

dydt

 

[thryll]

The output voltage is 5V @ 25mA max out of the controller
The relay is a solid state relay with snubberless triac output, 3 to 32 VDC input voltage range, voltage input, 0.05 to 25 ampere rms output current, 24 to 240 volt rms output voltage.

 

[wired1]

Are you sure the output of the controller is the right type? There may be several types available (eg. analog 0-10, digital PWM, or dry contact). Check your product lit for types of control outputs available. If you have an analog output, I don't see why it wouldn't work.

 

[jraef]

It sounds as though perhapse the burden on your SSR signal input is too high for the controller signal output, i.e. the SSR is trying to draw 50ma and your controller can only put out 25ma. If so you will need some sort of a signal conditioner in between. Your SSR should have a spec on the signal input burden. Quando Omni Flunkus Moritati

 

[buzzp]

Just as I thought. Your temp controller has a TTL type output.
Are there any other outputs available on the controller, ie relay? If not, then you will likely have to drive a transistor base to turn on the SCR (dont think you will find a relay coil of 5V that only requires 25mA). Good luck.

 

[jbartos]

Suggestion: Check with the temperature controller manufacturer tech support for proper interfaces.

 

[busbar]

Milliampere-DC measurements between controller and SSR should be revealing.

 

[thryll]

The input current max for this relay is 14mA

 

[Shortstub]

Shouldn't one first ask "What's the supply voltage?"

 

[wired1]

If the output is a TTL type, you may have to go back to the same company for the solid state relay. For example a certain heater control company I know of has "smart" SSRs that will only work with their controller when strapped with the "smart" control interface. You can outfit their controller with a different kind of output to make it work with other relays. I suspect you don't have the right match. Follow the advice of jbartos.