Mark's Antweight build

All things antweight

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Paulmchurd
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Re: Mark's Antweight build

Post by Paulmchurd » Thu Mar 22, 2018 11:43 am

Atleast nothing blew up!

I found another nice looking h-bridge. The dasmikro seems to have been taken off banggood.

https://m.ebay.co.uk/itm/Stepper-Dual-M ... =547517332

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MarkR
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Re: Mark's Antweight build

Post by MarkR » Thu Mar 22, 2018 7:49 pm

That H-bridge looks very tidy.I like the extreme low profile and that it's official rated to work with 3v3 logic levels. also benefits from actual holes in the PCB, unlike the Dasmikro which is compact but fiddly.

I could use one of those for weapon control.
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peterwaller
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Re: Mark's Antweight build

Post by peterwaller » Thu Mar 22, 2018 8:54 pm

I used those chips in my previous speed controller board I used one chip for each motor if you parallel the two drivers in each chip you get 2.4 Amp drive. The main problem using the chip direct was the are fairly large with 24 pins on a very narrow spacing so difficult to solder. The MX612 are much smaller with only 8 pins although they are limited to 9.6 v.

Paulmchurd
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Re: Mark's Antweight build

Post by Paulmchurd » Thu Mar 22, 2018 9:29 pm

Wouldnt using two of the chips be far to much for an antweight? When only 1 is needed.

I've ordered one off banggood. Cheaper then the one I posted. I'll give it a test and report back ... in a few weeks

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peterwaller
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Re: Mark's Antweight build

Post by peterwaller » Fri Mar 23, 2018 9:36 am

Back when that controller was designed some of us were using the pololu high power motors which had a stall current of 1.6 amps at 6 v.
So if you were running them on 8.4 v that's 2.2 amps and even higher on 3 cells hence the doubling up.

Paulmchurd
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Re: Mark's Antweight build

Post by Paulmchurd » Fri Mar 23, 2018 2:20 pm

Ahhh ok, is there a way to work out the stall currant other then putting a multimeter in a series and grabbing the wheels?

These n20 motors seem like a lucky dip.

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peterwaller
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Re: Mark's Antweight build

Post by peterwaller » Fri Mar 23, 2018 4:16 pm

That's as good a way as any if they don't quote it.
Apart from the ones I mentioned and a couple of 12v ones they are nearly all sub 500ma so should be OK.
See chart from my web site of the ones I have found.
http://www.antweightwars.co.uk/MotorSpecs2.pdf

Ant Ipodean
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Re: Mark's Antweight build

Post by Ant Ipodean » Sun Mar 25, 2018 12:25 pm

I like the look of that TB6612 board, but can it be connected directly to the PWM outputs from an RC Rx, or would there need to be some additional "circuitry"?
And if so, is it very complicated to set up?

Mike.

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Re: Mark's Antweight build

Post by Paulmchurd » Sun Mar 25, 2018 2:42 pm

You need to use a micro controller such as an Arduino or raspberry PI to act as the speed controller.

Someone correct me if I’m wrong.

An electronic speed controller contains a h-bridge, BAttery eliminator circuit and a micro controller. The controller converts the Tx/Rx PWM to a readable pwm by the h-bridge which then controls the direction and speed of the motors using switch’s.

These h-bridges are for people who are making their own ESC’s. Eventually with tinkering around with creating your own. You can buy all the individual components and produce your own Esc circuit board just like the ones on nuts and bots shop.

I’ve self taught myself by watching YouTube and reading website tutorials. It can be a little tricky to understand at first but once you get the hang of programming/connecting the circuit boards together it get easier. It’s been a lot of fun tbh learning how to make an ESC.

Here is a video of how to use the h-bridge.

https://youtu.be/u0Ft8SB3pkw

Ant Ipodean
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Re: Mark's Antweight build

Post by Ant Ipodean » Sun Mar 25, 2018 3:14 pm

Thanks for that link.
It just seems that an Arduino or raspberry pi board has far more functionality than is actually needed to link an RC Rx to an H bridge just to control 2 motors, so costs too much in terms of space and weight.
Providing the 5 volt supply is easy enough, but I wonder if the "micro controller" function just requires one or two resistors or capacitors, or is it more complex than that?
Mike.

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MarkR
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Re: Mark's Antweight build

Post by MarkR » Sun Mar 25, 2018 3:58 pm

Paulmchurd wrote:
Sun Mar 25, 2018 2:42 pm
You need to use a micro controller such as an Arduino or raspberry PI to act as the speed controller.
I don't need to. I want to. That's different :)

It's because I'm trying to do something more interesting with the IMU. If I can find a board which has all the bits I want (suitable IMU, radio and microcontroller), I will use that instead. So far I haven't found one, so I could build my own; if I do that, I'll add H-bridges to make it act as a speed controller too, and also a voltage regulator so it doesn't need a separate BEC.
Someone correct me if I’m wrong.

An electronic speed controller contains a h-bridge, BAttery eliminator circuit and a micro controller. The controller converts the Tx/Rx PWM to a readable pwm by the h-bridge which then controls the direction and speed of the motors using switch’s.
Nearly right. The H-bridge is usually driven by 3 signals - enable, forward and reverse. The micro pulses the enable signal (with a "duty cycle" pulse from 0 to 100% - different from servo pulses) and enables forward/reverse as necessary.

The signal from a normal RC receiver contains servo-pulses in the range 1000-2000us for "full stick left" to "full stick right" - at least, that's the typical mapping, although people can use programmable TX units to do whatever they want with them.
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MarkR
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Re: Mark's Antweight build

Post by MarkR » Sun Mar 25, 2018 4:01 pm

Ant Ipodean wrote:
Sun Mar 25, 2018 3:14 pm
Thanks for that link.
It just seems that an Arduino or raspberry pi board has far more functionality than is actually needed to link an RC Rx to an H bridge just to control 2 motors, so costs too much in terms of space and weight.
Absolutely correct!

Yes it does too much, to bridge an RC RX to H-Bridge. But the Raspberry Pi also has a built-in radio, so you can dispense with the RX completely. Some arduino-like boards also have a radio built-in.

I haven't investigated how programmable the RX modules are, I believe some are programmable (to a degree)

The RX probably has its own very simple microcontroller in anyway.
Providing the 5 volt supply is easy enough, but I wonder if the "micro controller" function just requires one or two resistors or capacitors, or is it more complex than that?
It's certainly not possible with resistors / capacitors. An ESC is a real thing, the rx modules don't drive much current, nor in a usable way to drive DC or any other type of motors.

The only reason it's possible to hook servos directly into the rx, is that a servo is really just a DC motor and gearbox *with its own ESC built in*.
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MarkR
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Re: Mark's Antweight build

Post by MarkR » Sat Apr 07, 2018 8:18 am

It is looking better now, but without much more functionality, I need a lot more time to work on the software, get the flipper made and stuff.

I also think I need some smaller / lighter battery pack, maybe will pick up a 180mAh 3S?

Mark
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Paulmchurd
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Re: Mark's Antweight build

Post by Paulmchurd » Sun Apr 08, 2018 11:47 am

The galaxy range of lipos seems to have a lot more range of sizes. I'll have a look for a link later.

Looks good. Very neat and tidy. Would be interesting to see your mixing code and comepare it to what I've done. Have you got a GitHub account?

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MarkR
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Re: Mark's Antweight build

Post by MarkR » Tue Apr 17, 2018 2:17 pm

Hardware is nearly finished, the flipper works mechanically (if not yet electrically)
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