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10-07-2006, 10:21 PM
| #1 |
| Rock Stacker Join Date: Oct 2004
Posts: 59
|  Ohms Law???
On the boards I seen someone use 3 - 1 watt 10 Ohm resistors in series on the mini servos what I need to know is if the main power for the stock servo is 7.2v on the 1:18 Nylints by using 3 - 1 watt 10 ohm resistors in series what does that lower the voltage too? I know they said it's safe but the person using it has a 6v servo. I'm not familar with Ohm Law so can someone tell me how many resistors & what kind I need to lower the voltage to 4.8v - 5v?
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10-08-2006, 01:24 AM
| #2 |
| Rock Stacker Join Date: Feb 2006 Location: Brisbane, Australia
Posts: 59
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Ohms law is V=IR V = Volts I = Current in Amps. ie 100mA = .1A R = Resistance By putting 3 x 10omh resistors in series you get 30 ohms. To find the resistence needed you need to know what voltage you want to drop. In your case 2.2v The only unknown is the current draw. But if u make it say 500mA that would be about half load on a 645 or such. (just guessing, not really sure) therefore you want to find out resistance. R = V/I V = 2.2v (Voltage you want to drop) I = .5A (current load of servo) so R = 2.2/.5 = 4.4 ohms With that calculation, are you sure that the resistors wern't in parallel?? To find the wattage of the resistor required - P=VI P = Power V = Volts I = Current P = 2.2 x .5 = 1.1w So, with the info u have given and the made up servo current draw, you would need a 4.4ohm 1w resistor. I hope that makes sense. Brad. |
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10-08-2006, 09:48 AM
| #3 |
| Rock Stacker Join Date: Oct 2004
Posts: 59
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Thanks Brad! That helps alot! I'm sure it was series. I'm guessing they were going with 30 ohms just to slow the servo down. Thanks again!
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10-08-2006, 10:27 AM
| #4 |
| TEAM MODERATOR   Join Date: May 2004 Location: Tennessee
Posts: 10,855
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Brad...you made my head hurt  I'll have to read that sober |
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