Running Sierra sound with lithium ion???

paul delany

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Hi folks I'm moving to battery power, my problem is I'm feeding the left and right track imputs on my Sierra board with the crest receiver motor +and motor - pcb pads In order to give the Sierra a reference voltage, but?? As Greg said in his post anything above 12v and the sound chips are over heating, tried to use a variable resistor set for 30 ohms but varies too much,, and help appreciated please.
 

GAP

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Hi folks I'm moving to battery power, my problem is I'm feeding the left and right track imputs on my Sierra board with the crest receiver motor +and motor - pcb pads In order to give the Sierra a reference voltage, but?? As Greg said in his post anything above 12v and the sound chips are over heating, tried to use a variable resistor set for 30 ohms but varies too much,, and help appreciated please.
A "buck converter" would be you best bet.
This one is adjustable and take wide range of input voltages.

 

paul delany

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A "buck converter" would be you best bet.
This one is adjustable and take wide range of input voltages.

Hi OK, I need some explanation here as I thought I understood the Sierra board basics? How is the motor v output over stressing the sound chips? What am I missing? The start up voltage for a shay motor is roughly 9 volts? What am I missing here?
 

paul delany

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Hi OK, I need some explanation here as I thought I understood the Sierra board basics? How is the motor v output over stressing the sound chips? What am I missing? The start up voltage for a shay motor is roughly 9 volts? What am I missing here?
 

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paul delany

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Track voltage is 14.5 or what ever, motor + and motor - are feeding my Sierra track pickup imputs, so why is it over driving the sound processor S??
 

PhilP

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The simple answer would be to use a '3S' rather than a '4S' battery pack..

That way you would not exceed the 12V limit of the sound card.

Your motor is fed a PWM signal. - The full 14.5V but switched on and off, for different amounts of time (mark-space ratio) it is this that controls the motor speed.

PhilP
 

paul delany

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The simple answer would be to use a '3S' rather than a '4S' battery pack..

That way you would not exceed the 12V limit of the sound card.

Your motor is fed a PWM signal. - The full 14.5V but switched on and off, for different amounts of time (mark-space ratio) it is this that controls the motor speed.

PhilP
Hi Philip wow I didint know that at all, so I can't step down the voltage to 12 v with a 5 watt 30 ohm resistor then?
 

PhilP

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Hi Philip wow I didint know that at all, so I can't step down the voltage to 12 v with a 5 watt 30 ohm resistor then?
No, because the voltage across the resistor will depend on the current flowing through it, so will vary, rather than being a constant value.

As the load on the motor varies, the current will change through the resistor (which is fixed) so the voltage will vary.

PhilP
 

paul delany

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No, because the voltage across the resistor will depend on the current flowing through it, so will vary, rather than being a constant value.

As the load on the motor varies, the current will change through the resistor (which is fixed) so the voltage will vary.

PhilP
Hi PhilP I'm greatful for you explaining the finer detail, 30 years ago I worked in a r+d lab with access to ossiloscopes etc, I didint know that the motor voltage was a pulsed one, so I guess il leave the motor voltage feed disconnected from the Sierra imputs and have no sense voltage and just be happy with the chuff sound affect.
 

paul delany

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Hi PhilP I'm greatful for you explaining the finer detail, 30 years ago I worked in a r+d lab with access to ossiloscopes etc, I didint know that the motor voltage was a pulsed one, so I guess il leave the motor voltage feed disconnected from the Sierra imputs and have no sense voltage and just be happy with the chuff sound affect.
Or, a dc - dc buck converter at the initial pwr imput.
 

Fred2179G

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I used a similar converter in a tram that had a Lithium Ion 4S battery producing up to 16V when fully charged. My 12V ESC did not like that, so the converter keeps it happy. The tram is quite slow though!