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Easy Q if you have a multimeter

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so I want to create a DC to DC adjustable voltage power supply. I assume all i will need is the resisters. but, I don't have a multimeter, yet. In the mean time I was hoping somebody can give me the resister values for the following Voltage output:
1.5
3.0
5.0
6.0
9.0
12.0
I will be using two of the batteries in series pic of batteries below.
Amazon.com: Energizer Battery 12 Volt, Electronics.: Electronics
Ill be useing a DIP switch
please help me.
 

MikeMl

Well-Known Member
Most Helpful Member
How much current are you expecting to draw at the various output voltages?
 

Sceadwian

Banned
Resistors make horrible voltage regulators, why are you using a battery like that? The whole idea screams 'bad' to me. If you want a variable voltage source buy a variable voltage regulator IC a pot to control the voltage and a few caps for the input and output, and feed it from a 12V DC wallwart supply.

Even if your load is a static one like a bulb or a small motor using a resistor for 1.5 volts will waste over 90% of the power from the battery directly as heat, the battery would hardly last long enough to be useful, and the run time from that 12V is probably a little worse than a 9volt battery, meaning pitifully short.
 

audioguru

Well-Known Member
Most Helpful Member
Energizer's datasheet for the tiny 12V battery has its minimum recommended load resistance of 20k ohms. Its current at 12V into 20k ohms is only 0.6mA which is almost nothing. Its voltage drops as it is used and will be 10V in 50 hours.
 

audioguru

Well-Known Member
Most Helpful Member
You do not use a voltage divider to feed an LED. You use a single series resistor to limit the current.

But the tiny battery is too small.
At only 0.6mA an LED will be extremely dim. With a bigger battery at 25mA it will be fairly bright.
 
You do not use a voltage divider to feed an LED. You use a single series resistor to limit the current.

But the tiny battery is too small.
At only 0.6mA an LED will be extremely dim. With a bigger battery at 25mA it will be fairly bright.
Actually i was going to use two of them 24V.. but all i wanted to do was test 1-6 plus leds out at a time. don't worry about it people.. I'll grab a meter and do it myself. thanks anywayz
 
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