High Amps V Reg.

inwo

Joined Nov 7, 2013
2,419
power they can put into your motors and then the motors will be fine. If the speed controller can output 100A and the motor is only rated for 50A, then just limit how much throttle that speed controller will respond to so that it never provides more than 50% power. The

http://www.mikrokopter.de/ucwiki/en/BrushlessCtrl
Just now read this thread. Excuse me if I'm missing something.

Are you saying to ignore the voltage peaks and limit the average power?

Makes perfect sense to me.
A pwm is at its heart a regulator. Why build another.

My first thought before reading your post was to add capacitance to the output (if that's even practical) to limit peak voltage.

But then why bother? The motor will average the pulses just fine.
 

Thread Starter

mwalden824

Joined Mar 6, 2011
51
Here are some batteries has 16V and enough current, it may match what you need, but the price is high, if you can afford it then you will no need the regulator, 2N3055 or mosfets and heatsinks.
Thanks again for the reference, I'll check it out.

I read all of your posts and took what info was given then extrapolated from that to what you were trying to do and made my advice based on that.

The going with four 7500 mah cells VS six 5000 mah cells and reducing voltage was exactly what I was trying to point out.

Sorry if expecting you to do a bit of filling in the blanks from there was insulting to you.
Yeah, sorry. I was having a bad day not thinking clearly. Sorry. I appreciate your input.

1) Yes, a switcher can do this. It is roughly 2 kW. We designed 2kW rack mount switchers of various voltage/current combinations. It is possible. You did not say what internal power source was available?

2) No, you can't just add a couple of transistors to a linear regulator.

3) You should contact a power supply house to see if they have a product. Building this yourself from baseline starting point is virtually impossible.
Well I have built up a linear regulator with several pass transistors external to it and it works really good as far as regulation. Haven't tested anything else about it though. The design was based off of one I found on the internet using 7800 series linear regulators. I think I linked it in a previous post.

I'm just going to get a battery of the right voltage and current capability and avoid the regulation. Thanks for your input.

Just now read this thread. Excuse me if I'm missing something.

Are you saying to ignore the voltage peaks and limit the average power?

Makes perfect sense to me.
A pwm is at its heart a regulator. Why build another.

My first thought before reading your post was to add capacitance to the output (if that's even practical) to limit peak voltage.

But then why bother? The motor will average the pulses just fine.
Yeah, that's not exactly what I was talking about. See my ESC uses PWM to control the current through the phases of the BLDC motor by the duty cycle of the PWM. The MCU on the ESC is controlling this based of an analog input signal of 0-5V coming from the main board. My problem was I had a battery that was 25 volts full charge and wanted to step it down and regulate it for the voltage rail of the half bridges that control the current flow through the motor.

I have done further research and from advice in the thread and have come to the conclusion that a lower battery of the needed 16 volts but same Power capability will be my best option.

But I have one last question for everyone....
As the Lipo discharges the voltage rail on the half bridges will lower and the peak PWM voltage will lower there by decreasing the current flow through the motor. Should I reconfigure the ESCs to account for this my measuring the rail voltage with the ADC and increasing the PWM duty cycle as the voltage decreases? Or would there be a better way to do this?

Or maybe I don't even need to do this because as the voltage decreases the control loop inside the ESC would take care of it and increase the the duty cycle to keep the same RPM for the same input to the ESC, right?

The specs for the motor on the website I ordered it from are sketchy because it gives several different values for the same property. Like one part says the motor can handle 30 A max but then it says its rated at 1kW at 18.5V which is 1000/18.5V= 54 A. So I don't know. I will make sure my ESCs limit it to 30 A to be safe. I wish I could find better data for these hobby RC motors.

Anyway, thanks for everyone's help,
Michael Walden
 

Alec_t

Joined Sep 17, 2013
14,280
as the voltage decreases the control loop inside the ESC would take care of it and increase the the duty cycle to keep the same RPM for the same input to the ESC, right?
I would expexct a decent ESC to do that. Does its datasheet help there?
 

Thread Starter

mwalden824

Joined Mar 6, 2011
51
Would a 2N5302 TO-3 fill the bill ??
It wouldn't be capable of enough continous current unless I built individual step-down converters for each ESC/motor. But I am just going to use a smaller voltage battery. Thanks anyway.

I would expexct a decent ESC to do that. Does its datasheet help there?
Yeah it would. So I am going to do this now because I am building my own ESCs. The main reason I am building this quadrotor from scratch, or as scratch as possible is just to learn. I could easily buy the already made parts and have the quad built in a few hours probably, but I wouldn't learn much about design circuits, firmware, etc. which was the whole point of the project.

I might still buy a ESC so I can compare the results of mine to it. Not sure if they have datasheets though. I am sure they have some sort of spec sheet though.

But thanks for your input,
Michael Walden
 

MrChips

Joined Oct 2, 2009
30,713
Moderator's input to Michael Walden.

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