Heating Element Question

[sambedded]

Looks like something wrong with PSR. What exactly model do you have?

[drichards18]

Looks like something wrong with PSR. What exactly model do you have?

This is straight from the invoice.

Stock No: 97K7822
Manufacturer Part No: PSR-25
Description: POWER CONTROL MODULE; On State Current Max:25A; Supply Voltage Range:99VAC to 121VAC / 2.7VAC to 253VAC; Isolation Voltage:1500V; Supply Frequency:60Hz; External Depth:56mm; External Width:43mm; IC Generic Number:*PSR-25

[sambedded]

ОК nothing wrong with PSR. However according to spec it requires 250K pot. So you just using 50% of your dial.

[sambedded]

You can connect regular 500K resistor to your pot to make it 250K. See picture below

[drichards18]

You can connect regular 500K resistor to your pot to make it 250K. See picture below

From the looks of it that's just a 500k resistor connected in parallel, right?

I connect another 500k POT to the PSR terminals (which meant that 2 500k POTs were connected in parallel to the PSR). I took a reading of the resistance at the terminals and it was hovering around 250k when both POTs were at their highest resistance. When I turned on the power and took voltage readings at the element, it was only getting voltage when the original POT was at about 50% (I left the secondary POT at its' highest setting to simulate a regular resistor). This means that it gave an additional 10-20% on the dial, but still nothing before 50%. Is there another way to connect the resistor? Does a POT resistor react differently then a straight resistor? Should I use a higher resistor to get the action at the lower end of the dial, or just deal with it?

What is everybody else experiencing?

@MuleKicker - what do you see with the ones that you make?

[sambedded]

Pot doesn't differ from regular resistor.
If you have a multimeter - measure resistance of your combined pots - if you connect them properly - you should get 0-250K when rotating dial of one of them.

[drichards18]

Pot doesn't differ from regular resistor.
If you have a multimeter - measure resistance of your combined pots - if you connect them properly - you should get 0-250K when rotating dial of one of them.

Ok, that's what I'm getting. So I guess getting nothing on the lower half of the dial is normal? I was hoping for a way to "open up" that part of the POT for added control. I'm probably making this too big of a deal...

[rad14701]

Try that second pot you have there... It sounds like the original is defective under load if it tests good out of the circuit... Are you 100% sure it is linear taper...???

[drichards18]

Try that second pot you have there... It sounds like the original is defective under load if it tests good out of the circuit... Are you 100% sure it is linear taper...???

They both test good in terms of resistance and here is the exact line from the invoice:

• POT, COND PLASTIC, 500KOHM, 10%, 2W; Track Resistance:500kohm; Track Taper:Linear; Shaft Diameter:6.35mm; Shaft Length:22.23mm; Resistance Tolerance:± 10%; Power Rating:2W; Potentiometer Mounting:Panel; No. of Gangs:1 ;RoHS Compliant: No

I'll try the second one and let you know what happens...

[drichards18]

Try that second pot you have there... It sounds like the original is defective under load if it tests good out of the circuit... Are you 100% sure it is linear taper...???

They both test good in terms of resistance and here is the exact line from the invoice:

• POT, COND PLASTIC, 500KOHM, 10%, 2W; Track Resistance:500kohm; Track Taper:Linear; Shaft Diameter:6.35mm; Shaft Length:22.23mm; Resistance Tolerance:± 10%; Power Rating:2W; Potentiometer Mounting:Panel; No. of Gangs:1 ;RoHS Compliant: No

I'll try the second one and let you know what happens...

Just checked it with all 3 different configurations: the second POT, both POTs, and the original POT. I checked the voltage at the element and the resistance at the POT terminals. On all 3 tests the element was getting voltage when the resistance was at about 150k Ohms. It didn't matter what POT I was using. I even tried switching the terminals around - still the same results.

Should I throw a 235k resistor in parallel to get the full resistance to around 160k, which will give me full play on the POT dial, or is that a bad idea? I'm open to any other suggestions.

[drichards18]

Any updates or feedback?

[drichards18]

Still nothing, eh?

[sambedded]

Should I throw a 235k resistor in parallel to get the full resistance to around 160k, which will give me full play on the POT dial, or is that a bad idea? I'm open to any other suggestions.

Sure, try it. You'll get slightly un-linear tapper, but it's not a big deal.