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randino
Guest
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 Posted:
Mon Nov 28, 2005 9:35 am Post subject:
Lowering voltage to a brushless motor |
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I have a brushless motor powering a water pump for a PC. It starts up
@12 volts, but not 7. How can I lower the voltage to around 8 (BTW, I
have ground, +5, and +12 available)? I tried 5 Ohms of resistance, but
it still wouldn't start. Would a capacitor after the resistor help
anything? I'm guessing the motors resistance is not constant due to the
switching in a brushless motor. So would a capacitor make the input
voltage more stable?
I know all about PWM circuits, but I'm looking for something simple.
PWM is either expensive and bulky (around $30), or cheap (IC), but you
need to purchase 100 of them.
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Frank
Guest
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| Posted:
Mon Nov 28, 2005 9:35 am Post subject:
Re: Lowering voltage to a brushless motor |
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| The ATtiny series by Atmel... |
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Franc Zabkar
Guest
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| Posted:
Sat Dec 03, 2005 1:35 am Post subject:
Re: Lowering voltage to a brushless motor |
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| Quote: | I have a brushless motor powering a water pump for a PC. It starts up
@12 volts, but not 7. How can I lower the voltage to around 8 (BTW, I
have ground, +5, and +12 available)?
|
If the motor current is less than 1A, use an LM7808 regulator or
equivalent.
| Quote: | I tried 5 Ohms of resistance, but
it still wouldn't start. Would a capacitor after the resistor help
anything? I'm guessing the motors resistance is not constant due to the
switching in a brushless motor.
|
The motor's current would vary with the load. A resistor is not the
way to go.
| Quote: | So would a capacitor make the input
voltage more stable?
I know all about PWM circuits, but I'm looking for something simple.
PWM is either expensive and bulky (around $30), or cheap (IC), but you
need to purchase 100 of them.
|
Brushless motors use electronic commutation. I haven't tried it, but I
suspect that PWM would play havoc with the motor's Hall effect
sensor(s). At the very least you would need to smooth the output with
an L and a C.
-- Franc Zabkar
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neon
Joined: 25 Feb 2006
Posts: 593
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Wed Mar 08, 2006 1:02 pm Post subject:
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| the motor is a current device need it to do anything could care less about voltage except for breakdown. i will sugest to you an lm317 as a current source adjust it and let it run. |
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