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Subject: Re: [motm] Power Supply and Joystick advice

From: jwbarlow@...
Date: 2000-04-12

In a message dated 4/12/2000 11:50:51 AM, djthomaswhite@... writes:

>So what values in the voltage divider would I need to
>scale down to 10v?

It might be worth it to get a basic electronics book (like those ones they
have at Radio Shack, if not a better one).

Here's the general formula for a voltage divider:

Vout = Vin (R2/(R1 + R2))

where R2 is the resistor connected to ground on one side, and R1 is connected
to positive on one side.


10 = 15 (R2/(R1 + R2))
divide both sides by 15

2/3 = R2/(R1 + R2)

so, if you choose R2 to be 100K then R1 would be 50K -- I'd want to stay in
this (100K) range unless someone smart speaks up. There are other ways to
accomplish this, but I wouldn't use successive diode drops (like 0.6V each)
or a regulator (zener or otherwise) -- too much hassle. Especially since R2
might be a pot you already have as an attenuator, and you could just hang R1
off the back of that same pot PAiA style.