TinyTwo Speed Controllers

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Rapidrory
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TinyTwo Speed Controllers

Postby Rapidrory » Thu Feb 20, 2014 8:41 pm

Hi guys,

So 4 months ago when I started looking into antweights, I realized that there wasn't a whole load of small 2 channel ESC's available, and those which were costed far more than I had expected. So I thought, "I know, i'll just make my own! How hard can it be?"

Well, 4 months later having spend almost 100 hours laying out boards, hundreds more sifting the internet for components, learnt PIC assembler and spent hours fighting with that, and yet more time debugging... I've decided it was very hard! :P

Nonetheless, last night I finally got the prototype working, and today got it working well enough to do a demo.. so that's exactly what I've done!

Image Image

Video: http://www.youtube.com/watch?v=s3eNNzrkPNs&feature=youtu.be

I didn't want to mention it until I had a working prototype, as up until yesterday I had no idea if it would work!

Here are some specs.. I haven't had the confidence yet to test the current or voltage rating yet, so those are taken from the data sheets.

Max current per channel: 3.5A
Max Voltage: 18V
Dimensions: 21mm x 21mm
Weight: 4.5g with test cables, probably about half that without.

5V supply at ~1A to RX (will be 6V at ~2A on the next version)
Channel mixing done in firmware so can be used with cheap transmitters.

It's designed to accommodate the needs of a 4 motor pusher running at unnecessarily high voltages *cough*Haywire*cough*, hence the high current and voltage ratings.

There's a few bits on the design that need tweaking for the next version, and the firmware also needs a bit more work, but it's in a more or less usable state now. I've been trying to get it ready in time for the AWS otherwise I'd have nothing to run my Ants with!

If I were to do a batch of these once the design's been finalized, would anyone be interested in buying one? Having spent so much time developing it, it would seem a bit of a waste only to make a couple for myself... And if so, any ideas for other useful features whilst it's still in development?
Last edited by Rapidrory on Thu Feb 20, 2014 9:14 pm, edited 2 times in total.
Rory Mangles - Team Mangler

Robots: Too Many...

NanoTwo antweight speed controllers. (viewtopic.php?f=1&t=2128)

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Shakey
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Re: TinyTwo Speed Controllers

Postby Shakey » Thu Feb 20, 2014 8:44 pm

You know I'm interested in a few for my team :D
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Re: TinyTwo Speed Controllers

Postby haz » Thu Feb 20, 2014 8:50 pm

Image

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Re: TinyTwo Speed Controllers

Postby joey_picus » Thu Feb 20, 2014 9:47 pm

I'd definitely be interested in at least one or two :) would they have any compatibility issues with Corona recievers? I still have most of LYT's old electronics...
Joey McConnell-Farber - Team Picus Telerobotics - http://picus.org.uk/ - @joey_picus
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Shakey
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Re: TinyTwo Speed Controllers

Postby Shakey » Thu Feb 20, 2014 10:06 pm

It's designed to accommodate the needs of a 4 motor pusher running at unnecessarily high voltages *cough*Haywire*cough*, hence the high current and voltage ratings.


Hey I feel it is all completely necessary :P Especially the high powered motors and more wheels than any sane man would use!
Alex Shakespeare - Team Shakey:
AWS 44, 45, 49 & 51 Winner - Far too many robots to list!
I sell Antweight Parts, 3d Printing and Custom Designs!

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BeligerAnt
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Re: TinyTwo Speed Controllers

Postby BeligerAnt » Thu Feb 20, 2014 10:13 pm

Nice work Rory, although using a PIC and programming it in assembler is definitely doing things the hard way! :D

If the board is using two of the Toshiba motor driver chips in parallel it might not survive too long with 4 high power motors on 4S! Hopefully you've found some better driver chips.

Be aware of the issues of "placing on the market" in Europe any electronics-based product. This is why Peter Waller only makes his boards to order for friends. Offering stuff for general sale opens a whole can of approvals issues that you can't realistically comply with!

BTW I also have an open-source speed controller on the way... :)
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Rapidrory
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Re: TinyTwo Speed Controllers

Postby Rapidrory » Thu Feb 20, 2014 10:20 pm

Yeah, i chose the PIC cause it was small; hadn't really factored in the firmware :L

The motor driver chips are good for 30V at ~4A; it's the CMOS logic chips that limits it, so it should be fine up to 18V :L

And yeah, i'm only planning to sell to you guys with a lot of disclaimers :L

Ooh, sounds interesting! I hope it's slightly less difficult to build than mine :L
Rory Mangles - Team Mangler

Robots: Too Many...

NanoTwo antweight speed controllers. (viewtopic.php?f=1&t=2128)

marto
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Re: TinyTwo Speed Controllers

Postby marto » Fri Feb 21, 2014 12:39 am

Impressive. Everyone seems to say I could make an ESC for cheaper, which has more amps and more features but very few actually follow through.

Again nice work. Looks good and be keen to hear how it goes with testing.

Steve

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Re: TinyTwo Speed Controllers

Postby Rapidrory » Fri Feb 21, 2014 8:35 am

Joey wrote:...would they have any compatibility issues with Corona receivers?


If those receivers work with normal servos then should be fine; the ESC's only decoding the servo signals. Even if it did have a different servo signal, it should only be a case of changing 1 value in the program to calibrate it to the new signal :)
Rory Mangles - Team Mangler

Robots: Too Many...

NanoTwo antweight speed controllers. (viewtopic.php?f=1&t=2128)

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Re: TinyTwo Speed Controllers

Postby peterwaller » Fri Feb 21, 2014 10:00 am

First of all well done, having gone through this process myself I know just how much is involved.
As Gary says you have to be careful about openly offering them for sale with all the european legislation.
One word of warning the regulator part caused me more problems than I would have expected and you need to be very careful about the spec.
For instance if you rate the controller at 18v and the 6v regulatot at 2A you will be disipating 24 watts in the regulator assuming it is a linear type.
Also at 6v on two cell lipo you will be below the drop out voltage on normal regulators as the battery voltage dips below 8v so you may need and LDO regulator.
I use the LD29150 which is a low drop out (0.4v) 1.5A 5v regulator.
Another thing I halved the number of failiures in the field by fitting the battery leads with a non reversable connector so people don't reverse the batteries so often.
The question of compatibility with the Corona receivers and some others is that they output channels simultaneously and not sequentially as with standard receivers so depending how your firmware works they can cause problems.
Any way good luck with the venture you can't have too many controllers available.

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Rapidrory
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Re: TinyTwo Speed Controllers

Postby Rapidrory » Fri Feb 21, 2014 3:35 pm

Cheers for the advice Peter :)

Yeah, I had a look through your thread about selling ESCs, and very quickly decided not to sell them more officially :L

I've checked the specs on the voltage reg i'm planning to use: from the 'Output Short Circuit Current vs. Differential Voltage' graph, It shows that at 12V differential (so 18V input) it's capable of outputting about 1.1A. At a 6V differential voltage (so 12V input) where it would normally run on a 3 cell, it can manage a good 1.6A. It doesn't state for how long, and would heat up pretty quick dissipating 13.2W at 18V, but should would work OK if it was only running the Rx at that point. I'll have to run some more tests! I may have to say 18V as an absolute maximum voltage, with 12V or less being recommended. I'm using LDO regulators, and the drop out is 1.2V differential at 1A, so should be fine on a 2 cell. I tested it today running on 12V whilst driving a servo as well. My present setup has a 5V fixed regulator of the same type, and that barely got warm... although according to the power supply the servo was only drawing about half an amp, so it's not an ideal representation...

Yeah, I have a non-reversible lead on there too; I was more than a little concerned about plugging this thing in backwards after how long it took to make :L

Ah ok then no it wouldn't be compatible with the Corona Rx, as it relies on the pulses being sequential I'm afraid :-?

Haha, well I'm looking into getting a batch of 48 boards professionally printed and set up so I can re-flow solder a load at once; soldering up one by hand is bad enough! :L
Rory Mangles - Team Mangler

Robots: Too Many...

NanoTwo antweight speed controllers. (viewtopic.php?f=1&t=2128)

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Re: TinyTwo Speed Controllers

Postby joey_picus » Fri Feb 21, 2014 4:56 pm

I kind of figured that might be the case, I'll still happily buy a couple off you though, if you're willing to sell to me :) I might actually be interested in having them as a bare board with no leads, as that would save you time and effort and I find soldering weirdly relaxing...
Joey McConnell-Farber - Team Picus Telerobotics - http://picus.org.uk/ - @joey_picus
"These dreams go on when I close my eyes...every second of the night, I live another life"

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Re: TinyTwo Speed Controllers

Postby Hogi » Fri Feb 21, 2014 5:25 pm

will this model be fitted with a mixing switch? after seeing the effectiveness of epq I may have to think about building a four wheel drive ant at some stage.
Antweights: Hogi V7, Ant2D4, packapunch, skrub wrecker and naughty penguin, quick revive, T's.
Fleaweights: Fleadom fighter: 45, 360 noscope: 48, 49, (R)K-boom.
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Rapidrory
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Re: TinyTwo Speed Controllers

Postby Rapidrory » Fri Feb 21, 2014 5:37 pm

I theoretically could make it compatible, but not with out a pretty fundamental change to the firmware... It's taken me a month of coding so far to get this version working so unless i'm feeling particularly bored one day, there probably won't be a compatible version :L
Yeah, I was thinking of having an option with no leads; means you can solder in only what you need and save yourself some space/ me some time.. might even be slightly cheaper :L

Mixing switch? The firmware does the mixing atm, and I may do a non-mixing version if there's a demand for that, but there's no way of switching between the two once it's been programmed if that's what you mean..

I'm gonna try running some more scientific tests on them next week when I have a bit more time in the uni labs; I don't have the kit to run proper tests in my room. If anyone's curious to have a look at them, I should be running the prototypes in my two robots for the AWS. Hopefully will also be able to show that they're reliable if they last the day (..If :L). I
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NanoTwo antweight speed controllers. (viewtopic.php?f=1&t=2128)

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Re: TinyTwo Speed Controllers

Postby BeligerAnt » Fri Feb 21, 2014 7:43 pm

Nothing like 3 full days at Modelworld for stress-testing robots (and roboteers!) ;)

If you have a spare input pin on the PIC you could add 2 pads to the board, solder a link to short the pin low to disable mixing, leave it open to enable (default?). This does rely on having a spare pin on the PIC with an internal pullup resisitor.
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