Thanks for the reply. I know that you are right about the amps, but why would any power supply indicate that it was ready to output 22 volts, then NOT output 22 volts? How does the wire determine the incoming voltage? I've put that same wire up to 20-odd volts using the same ac-dc power source plus a PWM voltage regulator, and when I raise the voltage it gets up to a cherry red 350ºF quickly, without balking. This too-clever-by-half digital power supply is unable to do that. So I know that the wire is NOT a 6 volt wire. It's a whatever-voltage-I-want-to-apply wire that will do what I want, but this power supply, for whatever reason, won't deliver. I'll run some other tests tomorrow to make sure I've got my numbers right.

 

The results you are seeing is exactly what you would expect. The supply is limited to 6 amps therefore with a 1 ohm load the voltage will be limited to 6 volts.

If the supply were to output a higher voltage the current limit would be exceeded.

To test this, set the supply back to output 22 volts and place a 10 ohm load on the supply, and you should be able to output the full voltage.

 

Thanks for the reply. I know that you are right about the amps, but why would any power supply indicate that it was ready to output 22 volts, then NOT output 22 volts? How does the wire determine the incoming voltage? I've put that same wire up to 20-odd volts using the same ac-dc power source plus a PWM voltage regulator, and when I raise the voltage it gets up to a cherry red 350ºF quickly, without balking. This too-clever-by-half digital power supply is unable to do that. So I know that the wire is NOT a 6 volt wire. It's a whatever-voltage-I-want-to-apply wire that will do what I want, but this power supply, for whatever reason, won't deliver. I'll run some other tests tomorrow to make sure I've got my numbers right.

Would you expect the supply (any supply) to be able to maintain 22V across a short circuit?
Connect your wire to the supply so it is cherry red and measure the current through the wire. It will be a lot more than 6A.

 

Thanks for that note. A short is a very real possibility. I haven't had any problems-sparks, buzzing, whatever- but that is definitely worth a look. Particularly if it saves me from sending the PS back. My way to investigate it would be to dummy up a simplified version with a spare length of wire, 2 nails and a 2X4. Nothing around it. No hinges, no muffler tape, no springs. If that works right, and gives me the right output values, then you and the power supply are on the mark. Thanks.

 

You cannot get more than 6A from that supply and the wire that you have needs more than 6A. There are two solutions:
1. Use thinner wire. Thinner wire will get hotter at 6A than thicker wire.
2. Use a supply which can supply more than 6A.

This is not a fault in the power supply. It is doing exactly want it is supposed to do - what any 6A supply would do.

 

I don’t think there is anything wrong here except your understanding.

You said you hook it up to a nichrome wire and the most you can get out of the supply is 9V and 6A.

The specifications say the max output current us 6A.

So what is it that you think is wrong?

You do know about Ohm’s law, right?

Bob

 

I was right. You don’t understand Ohm’s law.

For a given load, you cannot set both the current and the voltage. You set one, and the load sets the other.

Your supply can deliver a constant voltage, OR a constant current, not both at the same time. No power supply can do that, it.

Bob

 

You won't get any argument from me about my understanding. I am satisfied with the power supply's amp output. The problem I'm running into now has changed a bit. I tore down and rebuilt the PS with an almost identical enclosed power supply, checked the values coming from the supply to the switches and the control panel(they were up to spec), and the problem now is that I can get the hoped-for voltage output dry, on a multimeter, and I can select and set the same voltage on the control panel prior to outputting for real to the nichrome element. But when I switch the output to the wire element, the voltage drops from 22vdc to 6vdc. Another commentator suggested that there could be a short fouling the circuit somewhere. That could well be the case, so my next step will be to reproduce the circuit with absolutely nothing around the wire: 2 nails in a 2 X 4, the springs, the wire, and connectors going to the PS. For what it's worth, I tried the heater a month ago with one of the enclosed PS's and a cheap PWM voltage regulator. Worked perfectly. I varied the voltage up to 10 or 12 or so, with 14.6 amps, and I got a hot wire going through steps from warm to about 400º F.

 

I was right. You don’t understand Ohm’s law.

For a given load, you cannot set both the current and the voltage. You set one, and the load sets the other.

Your supply can deliver a constant voltage, OR a constant current, not both at the same time. No power supply can do that, it.

Bob

Hm. OK, if that's Ohm's law, then it is right. However, what I need in wattage, with this 20ga wire, ain't much. According to the nichrome calculator, I should be able to get the right results- 14 watts- with 4 vdc and 4adc. So given Ohm's law, I should be able to hit the right temperature with what I have. Is that not accurate? I'm going to reduce the margin for error (shorts) and see what happens with a bare-bones nichrome wire later today. And I will make sure I'm setting it at constant current.

 

The results you are seeing is exactly what you would expect. The supply is limited to 6 amps therefore with a 1 ohm load the voltage will be limited to 6 volts.

If the supply were to output a higher voltage the current limit would be exceeded.

To test this, set the supply back to output 22 volts and place a 10 ohm load on the supply, and you should be able to output the full voltage.

That sounds like a good idea. I should have a 10-ohm resistor here somewhere. I admit, I haven't had practice using Ohm's law with resistance as well as volts and amps. This is as good a place as any to start.

 

Another commentator suggested that there could be a short fouling the circuit somewhere.

No he didn't. He was asking you what you thought would happen with a short circuit.
6V, 6A is what you will get with that piece of wire. If you want 22V across that piece of wire you will a supply which is capable of 22A.

 

So you are saying that any given power supply is only capable of a maximum voltage that is in parity with the amperage? So a power supply capable of 30 volts has to have an amp capability of 30 amps?

 

So you are saying that any given power supply is only capable of a maximum voltage that is in parity with the amperage? So a power supply capable of 30 volts has to have an amp capability of 30 amps?

No.
The values being numerically equal is a consequence of the nichrome being 1 Ohm. Had it been 2 ohms then you would get 12V at 6A.
Go study and understand ohms law.

 

OK, your conclusion matches the calculation in the Nichrome calculator. A 20ga wire 46cm long will create a resistance of approximately one ohm, and, as it turns out, the A and V values are more or less the same. The hair in the soup is that, at that wattage the wire should be putting out 400ºF. It isn't doing that. If it were doing that, I wouldn't be beefing about it. And I can see that it would be a real improvement to bone up on Ohm's Law. Point taken.

 

How do you know it isn't at 400°F? That is nowhere near cherry red. An ordinary domestic oven will do that temperature.

 

I'm using an infrared thermometer. The wire gets up to maybe 230º.

 

A question, is this for a foam cutter?

 

It's a plastic bender.

 

JFTR I said 10 ohm load, not 10 ohm resistor...if you use a resistor be sure it can handle 50 watts.

 

I'm learning. Thank you.