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Cooking with Resistors: Breakdown Voltage?

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DigiTan

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I bought one of those tiny 650v ballasts they use for miniature flourescent bulbs last year. Frankly, this thing hasn't seen the...light of day ever since ('little joke there, to lighten the mood) and I'd like to give it a nice workout.

Before jumping into things I wanted to apply a few resistive loads and see if I could verify the output is really the 650v, it's advertised to be. Since my multimeter is limited to 250Vrms I figured a voltage divider would be useful but now I need to know if this high voltage may cause any breakdown in the resistors. I'm not in the dark when it comes to resistor basics, but as far as breakdown goes, I don't know watts watts. :lol:

Would a resistor have a bright future dropping such a high voltage, or does the outlook seem dim? I need someone to shed some light on this situation.

(The resistors are 1/4W and/or 1/2W carbon film)
 
:: Scoffs :: I've heard of postcount whoring, but thoes last replies take the cake. I already know resistive heating, and Ohm's law for that matter. What I'm referring to is the dielectric strength of my resistors--which means the condition where my load resistance may or may not drop dramatically and (probably) do damage to my ballast. I came here for advice, not insults, so please read me very carefully.

Now that we're on the same page, I'll add that most likely (because of my meter) I'll be using a 1/3 or 1/4 voltage divider which means my largest resistor will be dropping 433 or 488V respectively--assuming the output is 650V. Are these high voltages pushing the limits of the carbon film or am I in the safe zone here? Also since we're on the subject, what's the composition of a typical carbon-film resistor. I know it's not just carbon, so what can I expect?

[edit]

Also, I plan on using resistors in the MΩ range--to keep my current under control.
 
Digitan as long as you dont exceed the 1/4 or 1/2 watt power rating of your resistors you should be fine..
 
DigiTan said:
as far as breakdown goes, I don't know watts watts.

It's that little pun that made me think you didn't exactly master 0hm's law. It seemed to suggest you didn't know how to calculate the resistor's dissipation.

I have no need for postcount whoring, believe me ;)

A nice day to you, sir. :roll:
 
If you need to know the ratings of something, why not look on its datasheet? Isn't that what datasheets are for?

Vishay's ordinary cabon film resistors' max voltage:
0.25W= 200V
0.33W= 250V
0.45W= 300V
0.55W= 500V.
 
audioguru said:
If you need to know the ratings of something, why not look on its datasheet? Isn't that what datasheets are for?

Vishay's ordinary cabon film resistors' max voltage:
0.25W= 200V
0.33W= 250V
0.45W= 300V
0.55W= 500V.
We did it again. :D
I was gonna let him do his own leg work, 'cause I thought he was a little over the top with Joel. Postcount whoring? Maybe my avatar should be a picture of me in a short leather skirt, standing under a streetlight.
What a disgusting image that conjures up. :roll:
 
Hi Ron,
I posted Vishay's ratings because they are clear. The one's you posted have 3 different voltage ratings for each resistor: 200V on weekdays, 300V on weekends and 400V on holidays. You need a calendar to use them. :lol:
 
Okay, sorry for being aprupt on that last post, Joel. I couldnt' tell if you were serious or trying to smug or something. :oops:

It guess it's a good thing I checked because I honestly expected the value to be up in the 1000V's. Just I'll be having a lot of resistors in series now.

Ron H, that last part was pretty funny.
 
DigiTan said:
It guess it's a good thing I checked because I honestly expected the value to be up in the 1000V's. Just I'll be having a lot of resistors in series now.

I'm presuming you're only wanting to do this for a short term test?, in which case don't bother getting carried away! - resistors don't instantly expire with too much voltage (within reason!), it's long term failure that's usually the problem.

Perhaps you ought to consider getting a better meter?, it must be an incredibly small and cheap one to only have a 250V range?, 1000V ranges are normal even on cheap meters.
 
Yep, I'm hoping to use them just long enough to take some readings and adjust the load. It's going to be a while before I'm in the market for a new meter (job searches not looking too good).
 
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