Voltage Regulator

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Voltage Regulator

Post by windu34 » December 30th, 2015, 5:39 pm

I am trying to use a 7.2V 2000maH NiCD battery to run my EV which comprises of a Castle Sidewinder 3 ESC and 4600kV motor. When I don't use a voltage regulator, it runs fine. I would like to regulate my voltage (and current) in order to get consistent results, but when I use the regulator, it seems to draw too much current and the motor kinda starts moving and then dies. I am reading a nominal amperage of about 8.5
Can anyone recommend any solutions or maybe a different Voltage regulator that might allow it to run better?

This is the one I am using now.
http://www.amazon.com/Efficiency-Conver ... or+step+up
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Re: Voltage Regulator

Post by iwonder » December 30th, 2015, 6:22 pm

Are you trying to do something like Battery -> Regulation -> ESC -> Motor?

Ideally, your ESC is controlling the speed of the motor directly but since BLDC motor controllers are dumb things it's possible it isn't.

You won't be able to regulate current in the system while at the same time regulating voltage, but just keeping a constant voltage is all you really need to do. It's a nice idea and it'll be neat to see if it works out in practice.

Now, what current does the setup (Bat -> ESC -> Motor) use normally, when it's trying to accelerate off the start line. Since it's probably going quickly and using a lot of torque, I'd guess that it's trying to draw more than 6A the boost converter you have now is rated for, so at present that's likely holding you back. Finding boost converters at a high current off the shelf doesn't seem to be easy (I couldn't find anything from my normal places at least..). However, the big issue with any type of switching power supply (especially boost converters) is the noise that's introduced to the ESC. They work by rapidly charging and discharging an inductor, this generates a sawtooth wave in the output, which is usually filtered by a large capacitor so it looks stable. However all those components have to be sized for the current drawn from the supply, and it just so happens that the ESC also works by switching currents on and off rapidly, long story short, all of this rapid switching of current all over the place is going to play havoc with the system. It might work, there's no telling, but it likely won't be very consistent, or might have issues under large accelerations.

All that being said, personally, if I were looking for a way to improve consistency I'd move to some form of closed loop control (and actually there is a closed loop system in the regulator, but you don't need to add the extra complexity). If you don't want to add an encoder and do speed or position control, maybe measure the battery voltage with whatever controller you're using and slightly change the speed you send to the ESC to compensate for a fully charged vs a discharged battery. That could replicate the idea of keeping a constant voltage without adding extra noise and complexity to the system.
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Re: Voltage Regulator

Post by windu34 » December 30th, 2015, 6:31 pm

iwonder wrote:Are you trying to do something like Battery -> Regulation -> ESC -> Motor?

If you don't want to add an encoder and do speed or position control, maybe measure the battery voltage with whatever controller you're using and slightly change the speed you send to the ESC to compensate for a fully charged vs a discharged battery. That could replicate the idea of keeping a constant voltage without adding extra noise and complexity to the system.
1. Correct.
2. That is our plan b, we are hoping to find an electrical solution.
What if- we tried a buck converter? Lowering the voltage slightly, but raising current?
http://www.amazon.com/DROK-Regulator-Co ... lator+buck
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Re: Voltage Regulator

Post by iwonder » December 30th, 2015, 6:36 pm

I'm a bit curious, why the electrical solution?

Regardless, a buck converter stands a better chance of working, and high current bucks are much easier to find. Your motor will have a lower top speed with the lower voltage.
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Re: Voltage Regulator

Post by windu34 » December 30th, 2015, 6:40 pm

iwonder wrote:I'm a bit curious, why the electrical solution?

Regardless, a buck converter stands a better chance of working, and high current bucks are much easier to find. Your motor will have a lower top speed with the lower voltage.
While testing it and making a graph of voltage vs speed I need to send via microcontroller would be perfectly viable, it would making testing a pain: having to charge the battery every 10 or so runs. Additionally, it is not a permanent solution and would complicate things as far as impounding laptop and having to adjust values right before running it.
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Re: Voltage Regulator

Post by iwonder » December 30th, 2015, 6:47 pm

windu34 wrote:
iwonder wrote:I'm a bit curious, why the electrical solution?

Regardless, a buck converter stands a better chance of working, and high current bucks are much easier to find. Your motor will have a lower top speed with the lower voltage.
While testing it and making a graph of voltage vs speed I need to send via microcontroller would be perfectly viable, it would making testing a pain: having to charge the battery every 10 or so runs. Additionally, it is not a permanent solution and would complicate things as far as impounding laptop and having to adjust values right before running it.
Wait what? Just use the microcontroller to measure the battery voltage and change the speed signal with a formula in the program, no laptop needed..

How does one solution require charging the battery less often than the other?
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Re: Voltage Regulator

Post by windu34 » December 30th, 2015, 6:54 pm

iwonder wrote:
windu34 wrote:
iwonder wrote:I'm a bit curious, why the electrical solution?

Regardless, a buck converter stands a better chance of working, and high current bucks are much easier to find. Your motor will have a lower top speed with the lower voltage.
While testing it and making a graph of voltage vs speed I need to send via microcontroller would be perfectly viable, it would making testing a pain: having to charge the battery every 10 or so runs. Additionally, it is not a permanent solution and would complicate things as far as impounding laptop and having to adjust values right before running it.
Wait what? Just use the microcontroller to measure the battery voltage and change the speed signal with a formula in the program, no laptop needed..

How does one solution require charging the battery less often than the other?
How would I measure the battery voltage with the microcontroller?
I didn't know you could do that. We use a multimeter in between runs
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Re: Voltage Regulator

Post by iwonder » December 30th, 2015, 7:01 pm

IIRC you're using an arduino, just use a voltage divider so the battery voltage is in the 0v-5v range and hook it up to an analog input, analog inputs measure voltage.
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Re: Voltage Regulator

Post by windu34 » December 30th, 2015, 7:07 pm

iwonder wrote:IIRC you're using an arduino, just use a voltage divider so the battery voltage is in the 0v-5v range and hook it up to an analog input, analog inputs measure voltage.
Oh wow, I never though of that! Thanks I will try it!
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