An Rc/electrical Question

[Punkrider]

I am making this discharger, i have completed everything except the resistor. I am trying to work out what resistor i will need. I have put my multimeter on the battery as it discharged, the relay switched off at 3.5 volts, but then after about a minute, the battery levelled out and stopped at 5.5 volts. What number number should i put into the calculation? 3.5v or 5.5v?

The resistor value is calculated by using:

R = Rr(Vc/Vr) - Rr

Where:

R is the resistor value

Rr is the resistance of the relay coil (92 ohms)

Vc is the cut off voltage required (5 volts)

Vr is voltage at which the relay releases (3.5 or 5.5 volts)

r = 92(5/3.5) - 92 = 39.43

r = 92(5/5.5) - 92 = -8.4

What resistor will i need, like 1/4 watt?

Cheers

Edited July 2, 2006 by Punkrider

[ogre]

If you can wait i will print off/show this post to my ep teacher for you. he flies helicopters so will know what what do etc...

[adamtrials]

If you can wait i will print off/show this post to my ep teacher for you. he flies helicopters so will know what what do etc...

I fly helicopters and dont know the answer sorry...

[Gavyn.]

right i'm not great at this but i'll give it ago.

to calculate the power over the circuit = p(W)=I/V

so p =I(?)/V

i = current so

i =v/r

i =5(?)/92

i =0.543a

p=0.543/5

=0.1086W

i think that means you need a resistor of 0.1-0.5w/40ohmfor 5.5 and 0.1-0.5w and -10

[adamtrials]

right i'm not great at this but i'll give it ago.

to calculate the power over the circuit = p(W)=I/V

so p =I(?)/V

i = current so

i =v/r

i =5(?)/92

i =0.543a

p=0.543/5

=0.1086W

i think that means you need a resistor of 0.1-0.5w/40ohmfor 5.5 and 0.1-0.5w and -10

I x V = W i thought?

[Gavyn.]

no idea it was abit of a geuss i was working on v=i x r and working the current out from the voltage and the resistance

[ogre]

My ep teacher says that a 1/4 resistor will do fine

[Punkrider]

Thanks man, much appreciated