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I originally posted this in this thred (HERE ) but thought that some that might be interested would miss it buried in another thread...

Many have stopped by their local Radio Shack store and noticed the famous LM317T adjustable voltage regulator and lots of 7805s, but, probably did not realize that all voltage regulators are actually adjustable. Any IC voltage regulator can be adjusted to a higher voltage than its fixed voltage (not exceeding its supply voltage) by just adding a couple of resistors to the circuit.

As an example, the 7805 (5 volt) voltage regulator can be usedas a 7 volt regulator for the Wing. In the Figure 1 below,assume 470 for R1 which means that a constant current of 10.6 mA will be seen between terminals 2 and 3. This constant current plus a regulator standby current of about 2.5mA will flow through R2 to ground regardless of its value. Because of this constant 13.1 mA, R2 can now be set to a value which will give us a constant2 volts across this resistor. A resistor value of 152 ohms or 150 (standard value) will give us the necessary 7 volts (actual about 6.97), With 5 volts across R1 and 2 volts across R2, a total regulated value of about 7 volts will appear across terminal 2 and ground. If a variable resistor is used for R2, then the output voltage can be easily fine tuned to any value greater than 5 volts up to nearly the supply voltage. The regulator standby current will vary slightly in the 7805 but 2.5mA will yield good results in the calculations. If an exact voltage is needed then R2 must be a variable resistor.

To make any fixed regulator adjustable, use the following formula:

V[suB]out[/suB] = V[suB]fixed[/suB] + R2(V[suB]fixed[/suB]/R1 + I[suB]stndby[/suB])
V[suB]out[/suB] = Desired output voltage
V[suB]fixed[/suB] = Fixed voltage of IC regulator (5 volts for 7805 or 1.25 volts for LM317T)

R1 = Assume any value from about 470 to 1K for best results

I[suB]stndby[/suB] = Standby current of regulator (use 2.5MA for 7805 or zero for LM317T)

Common Resistor Combinations for the 7805 regulator:

V[suB]out[/suB] R1 R2
6 Volts 470 100
7 volts 470 150
8 Volts 470 220
9 Volts 470 330
12 Volt 470 510

The famous LM317T adjustable regulator is really nothing more than a fixed regulator with an output voltage of 1.25 volts. Builders seldom need voltages below 5 volts so the 7805 regulator is a good choice and it even costs a little bit less than the LM317T and is almost always available.
 

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Monkey with a Football
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Another option is to simply add two series 1N4001 type diodes to float the ground where R2 is shown in your diagram.
That will sit you at 7.2V output.

Or you can just order 7807 regulators from DigiKey.com

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=BA17807T-ND

Bear in mind that all these regulators should have capacitors on the in put and output pins to ground. Minumum of 22 uf is recommended.

The input cap is to prevent electrical spikes from exceeding the max input voltage and the output cap is to help with regulation and prevent oscillation of the regulator.

This also helps keep the heat down on the regulators and heat damages these devices. Using a decent heat sink isn't a bad idea for the same reasons.
 

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Rudy wrote:
...Bear in mind that all these regulators should have capacitors on the in put and output pins to ground. Minumum of 22 uf is recommended.

The input cap is to prevent electrical spikes from exceeding the max input voltage and the output cap is to help with regulation and prevent oscillation of the regulator.

This also helps keep the heat down on the regulators and heat damages these devices. Using a decent heat sink isn't a bad idea for the same reasons.
That, of course, is the better way to do it.. but I didn't actually use the capacitors or heat sink... because... The fuel and temperature gages don't care about a little noise (I think there must be a capacitor in there anyway by the way the gage is damped) For most other applications it would be advisable to include the caps.... and the current draw for the GL1100 wasless than100 milliamps (if I remember correctly) so it really doesn't have to dissipate much heat; it doesn't get that hot... (stillworking and that was three years ago when I made it..) and yes, that was my source of the 7807 as well, but you won't find them at your local RS... If you happen to go back and read the link at the original post, it was in response to a mistake I made calling a 7807 a 7805... but a 7805 can be made to work... and I thought that this was worth mentioning (inspite of the mistake)since the 7805is so easy to find..
 
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