I scored 2 Honeywell UDC3000 Controllers and here is my plan.

I have come across 2 - Honeywell UDC3000 Digital Controllers which can use either Thermocouple (K) or RTD input, as well as several other configurations. The ouput mode is 4-20ma. These are 1/4"DIN controllers, so they are beefy units and will operate on 120vac.

Anway, my intent is to set one up for temperature control of an HLT and also use it for my Electric Smoker. When I construct the box, I will have an ouput recepticle for 120vac which will operate either the electric heating element of my HLT or the element of my smoker. I am purchasing the cabinet mounted connections for the "K" type thermocouples I will use. One will be installed in a stainless well in my HLT and the other in my smoker, so swapping out the operation will just be a matter of changing the setpoint temperature for controlling the heating element output then pluggin in the appropriate sensor.

I have searched for and fortunately found a 4-20ma to 3-32vdc ssr controller which I will use to control the output voltage for the elements.

I considered the AUBER PID Controller instead of the UDC3000, but these were free and I only need to pick up the 4-20ma to 3-32vdc controller which will run me about $95.00 with shipping. Once in my hands, I will have a friend duplicate the controller for me so if in the future I have need of another, it will not cost me so much.

Any thoughts or comments on my intent of use? Does anyone else out there have any experience with these units?

Salute!

It would be good if you posted the entire part number so we can see exactly how the controllers are configured. If there is a 4 to 20 mA output and you need to drive an SSR, instead of paying $95, two simple $.0.20 resistors may suffice.

The complete part number is: DC300C010020

This is configured as a 4-20ma output controller, so if you can provide the wiring detail for adding 2 - $0.20 resitors, I would appreciate it very much.

The device I plan on purchasing now is the "ssr". My original post was based upon purchasing a device that would convert the 4-20ma to 3-32vdc to control a ssr I currently have in my inventory, however this device makes it a lot cleaner. Your resistor addition is interesting and I would like to try it if it truely converts the 4-20ma signal to 3-32vdc.

Here is the link to the device I plan to purchase: http://www.wolfautomation.com/ProductList.aspx?query=rm1e23aa25



Thanks in advance for any information provided.

Salute!

Is this what I would essentially have to do to convert 4-20ma to 3-32vdc (apporximately scaled):

USING A MILLIAMP SIGNAL WITH VOLTAGE INPUT INSTRUMENTATION

Most instrumentation is set up to receive voltage. A commonly asked question is how to use a current signal with instrumentation set up for voltage. This is simply done by installing a resistor across the input terminals of the instrumentation. The value of the resistor is determined by Ohms law (V = IR). For example, installing a 500 ohm resistor will convert 20 mA to 10 volts (V = IR = .020 x 500). This is shown in Figure 7. The only other consideration is the zero offset. Since most current loops have a low end of 4 mA, there will be a zero offset. Using the same value resistor as above 4 mA will convert to 2 volts.

R=V/I

Where: R = Size of Resistor
V = Desired Voltage
I = Current

Example:
To Convert 4-20 mA into 2-10 V
R = V/I = 10/.02 = 500 Ohms

A 500 Ohm Resistor Would be Installed Across the (+) and (-) Terminals on the Instrumentation


In my case, I need 20ma to be 32vdc so - 32/.02=1.6k ohms. Is this correct?

Have you ever used this concersion process before?

I have done this with DDC controls where the output was 4-20ma and we were controlling 2-10vdc modulating devices. I installed 250ohm resistors (1 across the output terminals of the control board and 1 in-line with the output signal. This produced 2-10vdc control for the device directly from the 4-20ma output of the DDC controller.

Salute!

Actually the RM1E is not a 4 to 20mA to 3 to 32 volt converter. This is a device that can vary the power to the load based on the current input to it. If you look at the Transfer Characteristics in the Applications section of the data sheet you posted there is a chart that has input current vs. ourput power. If you look at 4mA input the device will deliver 0% power output, at 12mA it will deliver 50% power output and 20mA it will deliver 100% of the power output etc. The Honeywell PID, purchased in this configuration and used in conjunction with the RM1E is more or less a PWM controller. That is not necessarily a bad thing. I would have to look at the Honeywell PID users manual to see how it would actually work for you. A conventional SSR needs at least 3 volts to switch on to a maximum of 32 volts. Higher than that could damage the SSR. To use a conventional SSR we could use 20mA as our switch point and at 20mA have 3 volts mininum. At 3 volts and 20mA we have a resistance of 150 ohms. What this would give us, is at 20mA the SSR will turn on and deliver 100% power to the load and any other current less than 20mA the SSR is turned off. Does this make sense?

That 4-20MA input SSR is sweet, it incorporates a PWM function with SSR output in one package. That almost makes it too easy to setup a heating control loop, no pulse width calcs to do for heating percentages, just a scaled analog output.

Sawdustguy said:

Actually the RM1E is not a 4 to 20mA to 3 to 32 volt converter. This is a device that can vary the power to the load based on the current input to it. If you look at the Transfer Characteristics in the Applications section of the data sheet you posted there is a chart that has input current vs. ourput power. If you look at 4mA input the device will deliver 0% power output, at 12mA it will deliver 50% power output and 20mA it will deliver 100% of the power output etc. The Honeywell PID, purchased in this configuration and used in conjunction with the RM1E is more or less a PWM controller. That is not necessarily a bad thing. I would have to look at the Honeywell PID users manual to see how it would actually work for you. A conventional SSR needs at least 3 volts to switch on to a maximum of 32 volts. Higher than that could damage the SSR. To use a conventional SSR we could use 20mA as our switch point and at 20mA have 3 volts mininum. At 3 volts and 20mA we have a resistance of 150 ohms. What this would give us, is at 20mA the SSR will turn on and deliver 100% power to the load and any other current less than 20mA the SSR is turned off. Does this make sense?

Click to expand...

So assuming that one of the ssr's I currently have available is used instead of the device pictured above, i can install a 150 ohm resistor across the input terminals of the ssr and use the 4-20ma signal to turn on the ssr or apply power to the element @ 100%. This would work for me assuming of course that the ssr used does in fact turn on at the stated voltage. SSR's are something I have not used in my many years of DDC controls, I wish I had more knowledge of their function.

Is it safe to say that the SSR when energized will always provide 100% output to the element? My PID loop then would have to be able to modulate the on/off cycle to maintain the desired setpoint. Is this why the SSR is better than using a standard contactor or relay capable of handling the load /current of the element used.

Sorry for being so needy of information. I want to get this right the first time so I can move on to other DIY projects to better my brewing abilities.

Salute!

bmckee56 said:

So assuming that one of the ssr's I currently have available is used instead of the device pictured above, i can install a 150 ohm resistor across the input terminals of the ssr and use the 4-20ma signal to turn on the ssr or apply power to the element @ 100%. This would work for me assuming of course that the ssr used does in fact turn on at the stated voltage. SSR's are something I have not used in my many years of DDC controls, I wish I had more knowledge of their function.

Is it safe to say that the SSR when energized will always provide 100% output to the element? My PID loop then would have to be able to modulate the on/off cycle to maintain the desired setpoint. Is this why the SSR is better than using a standard contactor or relay capable of handling the load /current of the element used.

Sorry for being so needy of information. I want to get this right the first time so I can move on to other DIY projects to better my brewing abilities.

Salute!

Click to expand...

First of all I want to say I am jealous of your PID. After thinking about the PID and the SSR that can actually vary the power instead of turning off and on, it is actually pretty neat. With that being said, using a conventional SSR, it would modulate on and off to maintain the setpoint. When the conventional SSR is energized it will provide 100% output to the element. The neat thing about an SSR is that it is solid state. A relay or contactor physically makes or breaks contact and under high current demand can arc slightly and after a period of time needs the contacts to be cleaned or changed. An SSR doesn't have these contacts and lasts much longer. Never apologize for asking questions. Thats why HBT exists. Heck, I learned something from this too. I never realized an SSR that could vary the power instead of just switching existed. That was very cool.

What is really cool about the whole setup is that is has a ramp/soak feature in the controller and with the variable output, I can do some serious temp control. It should work out quite nicely with the smoker control too. I have had to adjust and re-adjust my temp controller on my electric smoker so many times that I began to dislike having to use it. Now I can program the UDC and walk away (not to far away though) until the program ends.

Thanks for your input and assistance. I should be receiving my components soon to complete the build and put this into operation. I will post pictures of the build process as I go forward.

Salute!

Pieced everything together (temporarily) and tested it out using the 3-32vdc SSR. I had to install 750ohm resitor across the SSR to get enough VDC output to control the SSR (more on that later). I hooked the panel to my electric smoker and test ran it with 3 different setpoints over a period of 1 hr.

With the 3-32vdc SSR I am able to maintain temperature within a 6 degree deadband (3 degrees above and below setpoint). This is not bad considering I only adjusted the controller's PID settings twice. I attribute the swing more to the element having to heat up and cool down then to the controllers ability to maintain a good PID control operation. The variable output SSR has not yet arrived, but I am going to install it and hope for tighter temperature control using it. The heating element will then never be totaly on or off during operation.

I used a NEMA 1 enclosure (RED) to install the controller, SSR, terminal strip, inline fuse and system toggle switch. I added a GFCI recepticle (also RED) to the back or bottom of the control box so I can plug my devices into the set-up easily. When the variable SSR arrives and I get it installed, I will post some pictures.

Salute!

Here are a few pictures of my build so far. It is not complete, but it is functional at this time for an electric smoker.





When the new Variable SSR, fuse holder and system switch are installed I will post final pictures.

Salute!

I got the variable output SSR and it is sweet! I hooked it up and tested on a small pot of water using a heating plate. I had the water to temp. within a few minutes and the controller maintained a 1 degree F. deadband. That is 1/2 degree above or below setpoint.

I used my DVM to monitor the voltage output to the heating element and it would ramp up and down to maintain a consistent temperature.

I am very impressed with the ability of this controller and device in maintaining setpoint so closely. It was a small test sample, but I believe the results will be close to the same for the whole volume which I will test this weekend.

I think it will perform just as well on my electric smoker as it does with the HLT.

Salute!

bmckee56 said:

I got the variable output SSR and it is sweet! I hooked it up and tested on a small pot of water using a heating plate. I had the water to temp. within a few minutes and the controller maintained a 1 degree F. deadband. That is 1/2 degree above or below setpoint.

I used my DVM to monitor the voltage output to the heating element and it would ramp up and down to maintain a consistent temperature.

I am very impressed with the ability of this controller and device in maintaining setpoint so closely. It was a small test sample, but I believe the results will be close to the same for the whole volume which I will test this weekend.

I think it will perform just as well on my electric smoker as it does with the HLT.

Salute!

Click to expand...

I am pretty impressed. I want one of those PID's too! Nice wiring and packaging job! You seem to have this well in hand. Very nice job.