A/R II R-24 0.1ohm 7w WW (NI??)

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Hi;
Quick question for those who know, R24 on the Atari A/R II is a 0.1 ohm 7w WW resistor, is it a non-inductive resistor?
Thanks
Jeff
 
Hi;
Quick question for those who know, R24 on the Atari A/R II is a 0.1 ohm 7w WW resistor, is it a non-inductive resistor?
Thanks
Jeff

There's no AC component running through it, so intuitively I'd say it doesn't matter.
 
Hi;
Quick question for those who know, R24 on the Atari A/R II is a 0.1 ohm 7w WW resistor, is it a non-inductive resistor?
Thanks
Jeff

R24 is a current sensing resistor so it does NOT need to be a non-inductive resistor. It is intended to tell the voltage regulator when you have a shorted output or too much load on the supply.

It does have quite abit of current going through it -- make it as large as possible for heat dissipation.

Ed
 
R24 is a current sensing resistor so it does NOT need to be a non-inductive resistor. It is intended to tell the voltage regulator when you have a shorted output or too much load on the supply.

It does have quite abit of current going through it -- make it as large as possible for heat dissipation.

V = I R + L dI/Dt...

If it's inductive, than change in current will make the reg think that more current is being drawn that really is, and destabilize the feedback loop. The TTL load should be *relatively* constant once the board is powered up, but if the designers thought inductance was important enough to put an NI in the circuit, he should do the same.
 
V = I R + L dI/Dt...

If it's inductive, than change in current will make the reg think that more current is being drawn that really is, and destabilize the feedback loop. The TTL load should be *relatively* constant once the board is powered up, but if the designers thought inductance was important enough to put an NI in the circuit, he should do the same.


Huh?
The circuit says the resistor should be WW...but does not say anything about NI. WW's are nearly always used in current sensing positions as they can handle the current and heat with minimal change in value. NI's are typically used in circuits where frequency is important.

In more than 25 years, we have never used NI resistors in any of our linear supplies and there is absolutely no reason to put an NI in this type of a circuit. This is merely a high current sensing resistor and nothing more. This part is intended to detect -large- current draws (i.e. dead short) and the WW's inductance has almost no play in this particular circuit at all. The minute amount of inductance that a standard WW has would introduce would have a negligable on this circuit.

Now, if this was a tank circuit or used within an audio circuit....
 
It is non-inductive.

The current going through it is not constant, so it does matter.

For all intensive purposes :D what AC component that would be associated with a change in power demand is negligible in the circuit. So no, it doesn't matter.
 
Ok;
So the consensus is a normal WW will suffice!?!?
Thanks and have a Merry Christmas (PC-happy holidays)
Jeff
 
For all intensive purposes :D what AC component that would be associated with a change in power demand is negligible in the circuit. So no, it doesn't matter.

You keep saying AC... but you don't need alternating current for inductance to matter. Inductance relates to any changing current.
But I have to agree with Ed here, as the current shouldn't be changing so rapidly here that a small inductance would make any difference. It's more important that you use a resistor that can handle the temperature and dissipate the heat. That's why it calls for a wirewound.
 
For all intensive purposes :D what AC component that would be associated with a change in power demand is negligible in the circuit. So no, it doesn't matter.

#1. That's "intents and purposes"
#2. We're talking about TRANSIENTS not AC vs DC, but I guess the power on transient is 'negligible' to you, and you don't care if the feedback look goes unstable...
 
#1. That's "intents and purposes"
#2. We're talking about TRANSIENTS not AC vs DC, but I guess the power on transient is 'negligible' to you, and you don't care if the feedback look goes unstable...

#1. Guess you missed the other thread where we were goofing on another KLOV'er.

#2. I'll give on the AC reference. When I say AC I mean (A) change in (C)urrent. :D But I'd like to see the scope trace that shows how the feedback loop goes unstable and the AR bursts into flames because we didn't use a non-inductive resistor. This is just silly.
 
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