Controlling heater with rheostat and fotek ssr

[xboxhaxorz]

I have a 220v 500w heater that i want to be able to control with a 25 amp DA fotek relay along with a 5 amp fuse. I have a potentiometer that i was using, but the ssr light would not come on when i wired it and i am not quite sure if i actually need to get a rheostat, the fuse is bypassed during this test.

source: http://www.auberins.com/index.php?ma...roducts_id=332

[budm]

Re: Controlling heater with rheostat and fotek ssr

Show us how you wire up your circuit.

[Longbow]

Re: Controlling heater with rheostat and fotek ssr

You are on the right path with a SSR, although this term is too general. Heater control is a huge subject in most industrial manufacturing settings. The 2 possible methods of controlling a high wattage heating element are phase angle control and zero cross firing. Usually a phase angle fired SCR is chosen for small load applications but it creates lots of RFI. Most large scale heating control is done using zero cross firing of back-to-back SCR's. Separate control circuits are used to drive a dual SCR block, which must have a heat sink. The controls need not be complicated if they are open loop. Industry standard is called a 20 mA control loop and all heating control SCR blocks will accept that control signal. Going up in expense, a closed loop controller can be plugged right in to the same SCR block. You will want a much more robust fuse in these cases along with MOV protection for the SCR's.

[budm]

Re: Controlling heater with rheostat and fotek ssr

The question is, are you trying to just turn the heater on and off or you are trying to be able to adjust the amount of heat from the heater?

[xboxhaxorz]

Re: Controlling heater with rheostat and fotek ssr

I will provide circuit information when i get back to my equipment

Initially i purchased this item http://www.ebay.com/itm/161166795326...84.m1439.l2649

I felt though the quality of this was not too high and may be the culprit if failure arises so i looked into the SSR option

The heater being used is a 60 x 60 ceramic heater, its actually 230v, 500W and 750c

I went with a ceramic fuse at 5 amps, when i tested another heater which is 250w using a kill o watt at 120v it was using less than an amp but due to voltage worked at 70w

My end goal is to have a controllable analog heater to raise and lower the temperature

I have a PID that i used, but for this particular product i dont want it digital

[budm]

Re: Controlling heater with rheostat and fotek ssr

"230v, 500W" If the heater is made for 230V, the current draw will be 500W/230V = 2.17A.

"which is 250w using a kill o watt at 120v it was using less than an amp" If this 250W heater is made for 230V then heater resistance will be 211 Ohms so the current draw with 230v applied = 1.09A, but the same heater (211 Ohms) at 120V then current draw will be 0.57A. So you need to know if the heater is made for 120 or 230V operation.
If the resistance remains the same, double the voltage applied to the load will result in quadruple the Wattage.
So basically you need to vary the power using TRIAC (or back to back SCR to get full wave) with controller to be able to adjust the firing angle to give you variable heat you need. It should also have good RFI/EMI fllter to reduce the generated noise.
I would get the unit that have at least 50% higher capacity than the load requires.
That $4.99 EBAY 2000W SCR module does not look like it can handle 2000W, no filter, no protection, etc.

http://sound.westhost.com/lamps/dimmers.html

[xboxhaxorz]

Re: Controlling heater with rheostat and fotek ssr

the heaters are definitely 230v i THOUGHT i could use them at 120v but was wrong so i got a transformer which is rated for 500 watts so now i am operating them at the proper voltage

my issue now is that the SCR module i bought does not work, i figured it would not tolerate 2000w but at least 250w or 500w

i have about 5 pcs SSR relays http://www.amazon.com/40A-SSR-Solid-.../dp/B004HZLMTW that were lying around so i figured i could just use those instead of the faulty SCR to make it analog using a potentiometer

[budm]

Re: Controlling heater with rheostat and fotek ssr

SSR is fully on or fully off (it done using SCR or TRIAC for switching instead of electro-mechanical relay with mechanical contacts) so if you try to adjust the output with POT is not going to work.
SSR input control can be anything from 3-32VDC without burning up the Optoisolator inside is also isolated from the output circuit so it can be controlled by logic circuit.
The amount of the SCR or TRAIAC conduction time is done with RC Phase angle firing control circuit.
That one from EBAY, you can see the pot and R-C circuit for Phase angle firing control, as shown, it is a 2000W Dimmer.
We also do not know if the load side has to be isolated from the control side for safety or not for your requirement.

[xboxhaxorz]

Re: Controlling heater with rheostat and fotek ssr

I understand. So this is a special SSR then basically an SSVR as it mentinos? http://www.auberins.com/index.php?ma...roducts_id=332

It would be great if you could point out a product that will allow me to control the heater via analog without use of PID controller.

I found some information on this forum as well http://www.homebrewtalk.com/f170/pid...s-ssvr-429498/

[budm]

Re: Controlling heater with rheostat and fotek ssr

That SSVR is the high current dimmer module with Pot for adjusting the power applied to the load.
What do mean by via ANALOG, the pot is the analog which will control the output of the module. Are you talking analog output of the black box that put out variable DC voltage from 0~5VDC, 5VDC= MAX output of the module, 0V = no output? Clarify the word analog and what is it that you will use to control the module instead of using the Pot that comes with the module.
The pictures as shown for the connection and function is very simple:
http://www.auberins.com/index.php?ma...roducts_id=332

[xboxhaxorz]

Re: Controlling heater with rheostat and fotek ssr

Hi,

When i mean analog i mean using a dial knob versus using a digital PID

[redwire]

Re: Controlling heater with rheostat and fotek ssr

Check the Fotek SSR part number you are using.
Fotek have some (VA=adjustable series) that have a potentiometer input which does phase control.
Their (DA=on/off series) is for only switching loads on or off (zero cross).
I think you have the two mixed up.

[Longbow]

Re: Controlling heater with rheostat and fotek ssr

Seems like the OP is confused about what that product is and how it is used. The product detail indicates that it is a phase fired device, similar to a light dimmer and is capable of handling a load current of 25 amperes. You can use it to control either 120v mains or 240 volt mains.

The SSR device has a built it phase controller. In other words, it has the controller circuit built into the device and requires only the external pot. Very simple. Heater control IS done using "on-off" devices due to the high currents. Just mount the SSR on a heat sink and fuse it. My numbers indicate that the heater you desicribed will draw just over 2 amps @ 240v. So a 5 amp fuse would be sufficient. Use an industrial fuse like this:
http://www.littelfuse.com/products/f...lc/slc005.aspx

Most high power SSR devices can be used with a standard 20 mA open-loop controller available at the manufacturer's web site. PID controllers are closed-loop industrial devices and not needed for simple home projects. PID = proportional, integrative, derivative for those desiring extra credit.