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Author Topic: Miniature ESC  (Read 5199 times)

NigelW

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Miniature ESC
« on: January 04, 2012, 11:44:58 am »
Hi All,

I'm building a small scale 1/32 rigid inflatable as a daughter boat for my Dutch Courage tug. It's approx 220mm long and will use a scalextric motor pulling less than 5A.

Does anyone know of a fwd/rev speed controller very light and small that will do the job?

I've looked at the Mtroniks micro viper marine 10A but it's a little bulky for this job.

Ideally need something the size of a postage stamp and less than 10mm thick...

Any advice appreciated.

Thanks,

Nigel
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Stiggolas

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Re: Miniature ESC
« Reply #1 on: January 04, 2012, 12:30:18 pm »
The only things smaller than the Mtriniks micro 10 that I've seen are for brushless motor setups from the likes of Giant Cod and CMB. I'm considering a similar setup for my Magic Cat which runs a 180 motor at present. I'm not sure a scalextric motor would work, are they not 12v? You may be better off going small brushless with a 7.4v Lipo.
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Subculture

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Re: Miniature ESC
« Reply #2 on: January 04, 2012, 12:44:21 pm »
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Patrick Henry

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Re: Miniature ESC
« Reply #3 on: January 04, 2012, 12:46:33 pm »
Have a look at ACTion Electronics Pico esc, it's tiny, and even smaller minus the case.

http://www.action-electronics.co.uk/speed.php
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cuppa

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Re: Miniature ESC
« Reply #4 on: January 04, 2012, 01:02:13 pm »
Maybe one of the GWS brushed speed controllers would do?

http://www.moormodels.co.uk/acatalog/GWS_SPEED_CONTROLLERS.html
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andyn

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Re: Miniature ESC
« Reply #5 on: January 04, 2012, 01:10:10 pm »
Or, the smallest Ive ever seen at rating would be a Ripmax xtra 7
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andrewh

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Re: Miniature ESC
« Reply #6 on: January 04, 2012, 01:15:26 pm »
Nigel,

Every servo contains a tiny ESC, and the smaller the servo the smaller the esc - how about 5mm square and fractions of a gm?

There are disadvantges of using them, but they are readily available and WILL do the job.  I have used them with all types of motor up to 385s with success.

There are many sites detailing how to replace the "pot" with either 2 fixed 2.5K resistors or (as I do) a 5K trimmer pot salvaged out of equipment.

Don't know if this will fill your requirement - but it does tick the small box :}
andrew
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NigelW

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Re: Miniature ESC
« Reply #7 on: January 04, 2012, 01:34:37 pm »
Thanks very much to all who posted a reply. I'll digest these tonight and I'm sure at least one of them will do the job. I'll post a note back to let you know how I get on.

Loads of info on this forum - THANKS AGAIN
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Sven

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Re: Miniature ESC
« Reply #8 on: January 04, 2012, 02:51:06 pm »
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andyn

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Re: Miniature ESC
« Reply #9 on: January 04, 2012, 07:31:03 pm »
Quote from: andrewh on January 04, 2012, 01:15:26 pm
There are many sites detailing how to replace the "pot" with either 2 fixed 2.5K resistors or (as I do) a 5K trimmer pot salvaged out of equipment.

I just find the sweet spot in the pot, cyano it in place and snip the arm off. Micro servo pots are small enough to tuck out the way.

Andy :-)
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malcolmfrary

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Re: Miniature ESC
« Reply #10 on: January 05, 2012, 09:26:35 am »
Quote from: andrewh on January 04, 2012, 01:15:26 pm
Nigel,

Every servo contains a tiny ESC, and the smaller the servo the smaller the esc - how about 5mm square and fractions of a gm?

There are disadvantges of using them, but they are readily available and WILL do the job.  I have used them with all types of motor up to 385s with success.

There are many sites detailing how to replace the "pot" with either 2 fixed 2.5K resistors or (as I do) a 5K trimmer pot salvaged out of equipment.

Don't know if this will fill your requirement - but it does tick the small box :}
andrew
Since the output transistors on the servo boards are only rated for usually under 1A, I suspect that the 385s must have been running on very low loading giving unexpectedly low current drain.  A normal servo motor pulls about a half amp.  It might be worth considering just what performance is required, and reconsidering the motor.  Is reverse really vital?  Some of the high current flight ESCs are really tiny.
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NigelW

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Re: Miniature ESC
« Reply #11 on: January 05, 2012, 12:14:15 pm »
I'd thought about a micro flight esc but reverse is actually quite important for manoevring the boat under the crane. High current is less critical and I'm hoping that the scalextric motor (18k rpm @12v) will run happily on either 6V or a 2s lipo albeit with reduced performance and lowish current drain.

So it looks like either adapting a servo esc with a pot and couple of FETs or the slightly heavy micro viper marine 10a might be the best options.

I'll let you know how it works out and post some photos.

Thanks,

Nigel

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andrewh

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Re: Miniature ESC
« Reply #12 on: January 05, 2012, 01:05:20 pm »
Nigel,

I use forward electric flight BL controllers for boat use by using another channel with a servo/microswitch to reverse the motor (change any 2 wires over) - unfortunately this needs more space and you may not have this available.

The Scalex motors will be very docile at 6V or so and will run happily on the amp of a standard size servo which as malcolmfrary correctly sez are rated at half and amp or so (fairly continuous).  We are always warned that the inrush current of a (standard) servo may be 2 to 3 amps.  FWIW the one I use with the 385 is actually out of a Futaba 1/4 scale servo and it was originally fitted with a beautiful 3-pole S400 type servo motor. 

 I have never (yet) let the smoke out and since I harvest them from archaic square-shaft servos I am crearly not pushing any envelopes, so I would suggest saving the FET output for the Mk2 version

andrew
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ACTion

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Re: Miniature ESC
« Reply #13 on: January 05, 2012, 01:10:14 pm »
Just a couple of comparative figures here:
ACTion P68A  Footprint 19mm x 27mm Weight without case 6g
MicroViper  Footprint 26mm x 26mm Weight 23g
Suit yourself.
DM
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NigelW

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Re: Miniature ESC
« Reply #14 on: January 05, 2012, 05:21:05 pm »
Hi there, thanks for the comparison. The P68 looks very favourable in all aspects except max current which at 1A will be too low for this motor. Please let me know if I've misunderstood the spec...

cheers,

Nigel
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john s 2

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Re: Miniature ESC
« Reply #15 on: January 05, 2012, 06:41:06 pm »
Nigel. Can i say that i dont think that a Scalectric motor will draw anything like 5 amps. Put it under load in your test tank and measure the current with an ampmeter. Hopefully the load will be little.Do leave it running for a while to ensure that overheating will not occur. John.
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NigelW

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Re: Miniature ESC
« Reply #16 on: January 06, 2012, 11:29:22 am »
Hi All,

the motor arrived today and I took a few measurements prior to selecting the ESC. it runs quite happily at anything above 1.5V (not great below this so not recommended for low voltage/low speed manoeuvrability unless using with a gearbox). Current draw is in the range of 100ma no load, rising to nearly 200mA under moderate load. Stall current at 7.4V is 1.6A and at 11.1V rises to 2A, so provided that the ESC has over-current protection, a 1A unit will be fine afterall - never assume anything!!!

All in all it's a good little motor and reasonably priced at £6 or so. Max rpm by the way at 12V is 18,000.

Thanks again for everyone's input. :-)

Nigel
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ACTion

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Re: Miniature ESC
« Reply #17 on: January 06, 2012, 11:36:06 am »
Quote from: NigelW on January 06, 2012, 11:29:22 am
so provided that the ESC has over-current protection, a 1A unit will be fine after all
Indeed it do! Please note that ACTion is closed for business now until Monday 16th January.
DM
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pompebled

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Re: Miniature ESC
« Reply #18 on: January 06, 2012, 05:57:19 pm »
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NigelW

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Re: Miniature ESC
« Reply #19 on: January 06, 2012, 06:07:44 pm »
Hi Jan,

It's certainly plenty small enough but unfortunately it has no reverse and a max input voltage of 5.5 which is a little on the low side.

Thanks anyway!

Nigel
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