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temp control ckt. for damper drive

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ret

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I need a circuit for modulating a control damper. I have a scrounged Honeywell damper control that is controlled by a 10 1/2 to 13 1/2 v. DC signal. I want to control it with a thermostat type circuit over a fairly small range....about 35 to 85 deg. F. I'm thinking maybe a thermistor based ckt. that would control a variable voltage regulator. Don't know how strong a signal it has to be, but from my experimentation, apparently it doesn't take much. I Put a 10k pot across a 13 1/2v. supply and drove it ok with a signal from the slider. The voltage regulator idea is probably overkill. Anybody have anything on hand or know where to find it? 120 vac will be available for power. Bob.
 
What is this thing, a motor with three wires and the third wire is a signal voltage?
Or are you varying the power to the motor through a slide pot?
 
Don't know too much about it's internals. It has 2 pair of wires coming from a terminal strip. Marking at terminals are 110vac for one pair and 24vdc at the second pair. When 110 is connected, the motor runs the actuator arm to one extreme and stops. I googled it and there are several options listed for control voltages. 10 1/2 to 13 1/2 v. is one of them and that is what it takes to stroke the one I have, so I need a temp sensing ckt. that can be adjusted for zero-and-span to equal 10 1/2 to 13 1/2 vdc.
 
That sounds pretty straightforward. So you need 10.5V when it's 35°F and 13.5V when it's 85°F - ?
 
you got it. I know that damper air flow is not porportinal to opening percentage, but I can take care of that to some degree by how I arrange the linkage and it won't be all that important in this application anyway. Now all I need is a schematic! I'm a competent tech when it comes to building or fixing things, but designing circuts is not my long suit.
 
I'll draw up a circuit for it later this evening... a TMP36GT9Z temperature sensor, an LM6132 op-amp, and an LM7815CT voltage regulator should do it easily. Do those 24Vdc terminals output 24vdc when you connect the 100Vac? If not, you are going to need something like this -
Digi-Key - T986-P5P-ND (CUI Inc - EPS180033-P5P)
 
Here you go. The first opamp controls the gain, the second opamp fixes the offset. R2 allows for some gain (span) adjustment, R3 allows for some offset. You should get the numbers you want when the pots are set right about in the middle.
 

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Thanks a lot Duffy. This looks like it should do the trick. No the terminals marked 24v. are strictly input terminals. I guess the reason they're marked such is that these units are set up at the factory for a lot of different DC control voltage options. Seems odd that there is no indication on the individual units as to what the control voltage is set for, but that's how it is. As for a power supply, I'm sure I can come up with one from my junk box or build one. I'll tap you again If I have any questions when I get it built.
 
Good luck, please post a pic when you get it built.
 
Damper control cktl

Duffy. Where do I get the TMP36GT9Z and LM6132 or equivalents? Tried several semiconductor sources on the net that I've used before, but no luck so far. Radio Shack's no help. Bob.
 
Digikey has them (they have a huge selection of components). Mouser and Newark should also be on your list.
 
semiconductor source

Thanks Duffy. I had gone to Digikey and used their search function to look for the parts and didn't come up with anything. Have since sent for their paper catalog and am waiting for it to arrive. I need to do the same for Newark. My inventory of electronics catalogs is getting so outdated they're not much use anymore. (anybody remember Burstein-Appleby in Kansas City??? One of their catalogs would probably be quite saleable on Ebay today!)
 
You weren't trying very hard. I just pasted them both in Digikey's seach engine again, and they are both still there, still in stock.
 
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