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What's this please? (Component Advice)

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gamalot:

--- Quote from: Abaku on June 13, 2021, 02:38:55 pm ---Hi all, I'm new to the forum. The burned resistor pictured is from a heated blanket controller. I'd rather replace the resistor than the whole blanket. I used the colour coding on the one below it (they're the same), with the help of a website, to help me find the resistor I needed on ebay. The discription for the listing is as follows:


--- Quote ---Metal Film resistors 60 different value, 5 different quantity
All resistor have 1/4W - 0.25W power dissipation and 1% tolerance rating

Values: 10 Ohm - 1 MOhm
Quantities: 1-10-20-50-100 pcs

--- End quote ---

I chose the 510 ohm resistor, and that's the one you see pictured, which is obviously very different in size but the bands look the same colour. Can anyone help me figure out which type of resistor I need to buy? Thanks  :)

--- End quote ---

Comparing to the size of other components in your picture, they look like 1W metal film resistors.

Nusa:

--- Quote from: gamalot on June 13, 2021, 02:56:41 pm ---
--- Quote from: Abaku on June 13, 2021, 02:38:55 pm ---Hi all, I'm new to the forum. The burned resistor pictured is from a heated blanket controller. I'd rather replace the resistor than the whole blanket. I used the colour coding on the one below it (they're the same), with the help of a website, to help me find the resistor I needed on ebay. The discription for the listing is as follows:


--- Quote ---Metal Film resistors 60 different value, 5 different quantity
All resistor have 1/4W - 0.25W power dissipation and 1% tolerance rating

Values: 10 Ohm - 1 MOhm
Quantities: 1-10-20-50-100 pcs

--- End quote ---

I chose the 510 ohm resistor, and that's the one you see pictured, which is obviously very different in size but the bands look the same colour. Can anyone help me figure out which type of resistor I need to buy? Thanks  :)

--- End quote ---

Comparing to the size of other components in your picture, they look like 1W metal film resistors.

--- End quote ---

I'd agree. Here's a resource that might help you: https://www.electricalengineering.xyz/sheet/resistor-power-rating-chart/

You could make what you bought work, since I see you have a quantity of them. Take four of them. Put two in series to make 510+510 = 1020 ohm 1/2 watt set. Do it again to make another 1020 ohm 1/2 watt set. Then put those two sets in parallel to make a 1020/2 = 510 ohm 1 watt assembly. Wattage is about surface area, it adds up serial or parallel; the math is simple with identical value resistors. Looks like you have enough space to squeeze that in if you do it right.

Or you could go buy the proper part.

Abaku:
Thank you both, I'll probably just buy a new one since they're pretty cheap, though I appreciate the suggestion, that's pretty smart  ;D Just to confirm, it's definitely 510 ohm I need yes?

tsmith35:
Just following up, the 2 varistors were located and replaced. Sizes were 2220 and 1210. Thanks again!

depot:
https://www.ti.com/lit/gpn/lm66100

I use this IC as an ideal diode and I think of using it as a switch too. But there's a hitch!

LM66100 has an input called ~CE. This is a comparator with the input voltage. Not only is it active low, but to turn off the IC, this pin must be equal to or above VIN (preferably above). This is much different from a typical logic level Enable pin!

Why is this? What's the typical application where the comparator is more useful? The datasheet has some notes about reverse current blocking, is that unique to the way this is designed? Curious.

Another silly thing about this is that the ST output is high-z when enabled and output low when disabled. But we never have a case to supply power to it and disable it, therefore this output is always high-z. I guess it's nice to have something that's logically-inverted from the output voltage.

But yes, I expect to use a mosfet or simple load switch instead.

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