windozeuser
Member
I don't get how to calculate the voltage division to divide the main voltage between n number of resistors. Can anybody please explain the principles and theory of voltage dividers.
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windozeuser said:I don't get how to calculate the voltage division to divide the main voltage between n number of resistors. Can anybody please explain the principles and theory of voltage dividers.
Megamox said:Looks fine, you could easily drop those down to quarter watt ratings without a problem.
Well he's using 3 different resistors and the biggest drop across any of them is 6v, with an I of 25ma, so max power in that would be 150mw..
Very Happy
windozeuser said:Ignoring TOTAL Circuit power consumption (which doesn't displace across any of the resistors. Each resistor has a power of less than 250 mW; so I can use 1/4 watt resistors safely.
Megamox said:Single resistor = 300mw/500mw = 60% of its maximum power rating
3 Resistors, Max power = 150mw/250mw = 60% of max power rating
So using 3 1/4 rated resistors gives the same margin of power useage as a single 1/2 watt which you would find acceptable, looks the same to me
Megamox
Why 1/2 watt? They're space hogs.
I can't provide any Kodak moments, but to put things in focus: 300mW is the total combined dissipation on R1+R2+R3. Right now, only the individual dissipations are in the limelight. In fact, you could crop things down to a 1/8th watt resistor for R3 and R1. Panning back to the diagram, windozeuser said his supply is 12V @ 25mA constantly, so our money shot is:mstechca said:so how does 150mW enter the picture when the wattage we are dealing with is 300mW?
The only way that 1/4 watt resistors can be used is to increase the resistance of at least 1 resistor.
If in your area, you can find any resistor that can handle 300mW and the maximum resistor rating is less than 1/2 watt, I like to see a picture. and don't show me a 1/4 watt one.
That's what I figured, but the thought makes me shutter. :lol:audioguru said:Gee, I didn't know they made resistors from old Kodak film.
Do they over-expose it to make poly-capacitors?