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Old Jun 19, 2013, 09:25 AM
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Mesa Falcon Fld, Arizona, United States
Joined Sep 2004
426 Posts
I just wanted to give a quick update. I have been able to get the low voltage detection circuit and code working. I also tested the device up to 8.2V. So far all has been well. I have been working on getting better low speed performance out of the motors, thereby reducing the deadband between forward and reverse. This is not an easy task. I have found a few things that seem to work well, though the size of the deadband is very dependent on the motor type that is used. So far I have been testing with 3 different motors. Of these, the geared motor has the largest deadband due to the large stiction forces of the motor.

This week, I will be testing it out on a smaller motor with a load, with particular interest in the low speed performance. I will also try and do some other load testing to see if the device failsafes and protection mechanisms work as advertized. Once that is done, I will be purchasing the next revision of the board and soldering up two more prototypes. These two will then go through some testing by me, then sent out to two early adopters to see if there are any further issues that need to be worked out before release.

Adam
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Old Jun 19, 2013, 12:05 PM
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Wichita, Kansas
Joined Jan 2004
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Excellent work, Adam!
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Old Jun 19, 2013, 12:46 PM
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Mesa Falcon Fld, Arizona, United States
Joined Sep 2004
426 Posts
Thanks Matt. I have taken a bit of a detour from modeling to learn electronics. I am not quite where I want to be yet, but I am getting there. I plan soon to be back into incorporating these electronics into my models. I have a few more electronic projects up my sleeve that I think will be of interest to the submarine community.

Adam
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Old Jun 19, 2013, 01:40 PM
Go small or go home
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Canada, SK, Regina
Joined Mar 2008
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The micro heli guys are regularly doing brushed to brushless conversions using one of these HK 3.5A brushless ESC

The micro heli conversions don't have an extra servo signal to drive the ESC, so they have to take the existing brushed motor PWM drive output, and condition it back into a servo signal, so it can control the brushless ESC. In the early days this required an additional micro-chip to do the signal conversion. But now the ESC is re-flashed so that it accepts the PWM drive output directly as input. Saves an extra circuit, wires, complexity and weight, etc.

So this little 3.5A brushless ESC is easily re-flashed with BHEL firmware so that it will accept a different input signal. The BHEL firmware also adds other new settings and goodies to the stock firmware. The BHEL firmware could also be easily modified to function as a reversible brushless ESC. In fact the BHEL firmware already has settings that can be configured to run the motor either direction. It would only need a change to the firmware to re-align the throttle end points and switch direction at center stick. I guess there just hasn't been anyone with an interest in doing so.

I know brushless motors don't appear to be that common in boating/subs. I'm not sure why, other than that's just how it's always been done. The same brushless power/efficiency/weight advantages for aircraft also apply to boats (well, except for weight, and maybe water cooling, which don't really apply at these scales). Brushless motors/controllers used to be prohibitively expensive, but now they're so common place that they can even beat brushed motor/controllers prices.

Anyway, there's loads of information out there regarding the BHEL firmware and how to flash ESCs. There are many different brands of ESCs (both different power capacity, and brushed/brushless) that can be easily re-flashed.

Have you considered creating an equivalent 'BBOAT' firmware that could be used to flash stock ESCs with reversible control? I think this would be a great benefit to the boating community (and others). It might even be cheaper in some cases to order a stock ESC and replace the firmware, then manufacture your own.

I suppose it would be impossible to convert a brushed ESC to reversing (brushless ESCs only need to re-sequence the order of the drive currents, not reverse the current flow). On the other hand, you could transform a single brushless ESC into a 3 output power module. One servo signal controlling 3 brushed (forward only) PWM motor outputs, or 3 high power search lights, or combinations of any of those. The possibilities for boat 'features' are endless.
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Old Jun 19, 2013, 02:08 PM
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Mesa Falcon Fld, Arizona, United States
Joined Sep 2004
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Ruzam,

I am a big advocate of brushless motors as well, but there are still a lot of brushed motors that are available. In fact in this small size (under 1.8A), I am going to guess that there are very few brushless solutions out there in this size.

This little controller came from a need for Tom and his little micro sub as well as a need that I have. These are little brushed motors that are under 4-8mm diameter. These are really what this controller are aimed for, but there are some larger motors that if can drive as well.

I do in the future, for my own use, want to build up a very micro brushless controller, smaller than the one that you posted with similar specs. It will be a long while till that happens, but it is in the works.

Adam
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Old Jun 19, 2013, 04:06 PM
Go small or go home
ruzam's Avatar
Canada, SK, Regina
Joined Mar 2008
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Ya, sorry, I didn't intend to try to steer you in different directions. I thought you might already be thinking down those lines already, so I threw it out there.

You're doing great work with your controller development! Don't stop! I'm looking forward to a micro reversible 'brushed' ESC as well.
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Old Jun 20, 2013, 09:43 AM
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Mesa Falcon Fld, Arizona, United States
Joined Sep 2004
426 Posts
Ruzam,

No worries, I did not take in in that fashion. Like I said, I eventually want to do a brushless controller. Not because there are not ones out there, but I want to learn how to do it. I also have some ideas that I want to incorporate as well that I do not see in other brushless controllers. Also, I want to add an option to have it so that it can be a sensored or sensorless system for true low speed performance, but I have a feeling that this is not going to be as straight forward as desired. So this is the reason why it is a ways off. I need to get this little guy done, then the pitch controller. After that, I am working some ballast tank controls. With that all done, then I am going to go after a full IMU device. All of these projects are building blocks to that final project. It should be fun.

Adam
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Old Jun 20, 2013, 01:14 PM
Go small or go home
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Canada, SK, Regina
Joined Mar 2008
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Do you have any unused IO pins on your micro controller? Like say, 2 per chance?

Here's what I'm thinking. Assign one unused pin as a second channel input (rudder), and a second unused pin as a slave output. On power up, check if there's a signal on the second input channel. If there is, then go into skid steer mode and mix rudder with the throttle output. The slave output (also mixed in skid steer configuration) would directly drive a second ESC in normal mode.

You would have one final ESC design that could either be used discretely as a single motor driver (default, as it is designed now) or chained as a slave with automatic throttle/rudder mixed skid steer. That would be a very versatile ESC.

If you have a two channel mixing mode, it might be possible to skip the slave output entirely. I'll have to brush up on my skid steer theory, but I think you can simply reverse the throttle/rudder channels on a second ESC to get the proper skid-steer control. Then you'd only need one unused IO pin.
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Old Jun 20, 2013, 01:34 PM
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Mesa Falcon Fld, Arizona, United States
Joined Sep 2004
426 Posts
I do have two pins available, but with a "computer" transmitter (I use that term very loosely), you should be able to do all the mixing in the transmitter just like you would do a V-tail. I may in the future look at doing something like your idea. I would need to see how much code space I had left. For the transmitter method, you would have to pull out your manual on how to do it as all transmitters are slightly different, but this would get your going with these initial devices as well as offer you much more versatility in the mixing options.

Adam
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Old Jun 21, 2013, 02:06 PM
TheyreComingToTakeMeAway!
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USA, ID, Coeur D'Alene
Joined Dec 2003
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I think one useful feature i might want to use, would be adjust the power curve end points in case one motor runs slightly stronger than the other, that way you can trim your boats "straight" without changing the center on the transmitter. If you try it om the transmitter, the motor will run constantly.
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Old Jun 22, 2013, 09:41 PM
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Mesa Falcon Fld, Arizona, United States
Joined Sep 2004
426 Posts
Well, time for another round of updates. I think that I can see the end in sight. I have one small board change (should be done tonight) and I am ready to order Rev X2 of the board. This should mean that in less than two weeks I should have the next boards to build up. I have also integrated all the sections of code and have tested all the features currently included. All tested out without any issues. I also tested out the over current protection (this is a hardware feature) and it also kept the device from letting out the smoke.

Adam
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Old Jun 23, 2013, 12:27 AM
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United States, NV, Las Vegas
Joined Aug 2011
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No smoke? I do not know what that will be like! :-)
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Old Jun 23, 2013, 11:14 AM
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Mesa Falcon Fld, Arizona, United States
Joined Sep 2004
426 Posts
You soon will my friend, soon. The end is in sight.


Adam
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Old Jun 23, 2013, 08:00 PM
George Jure
Hamilton, Ontario
Joined Aug 2005
282 Posts
Hi Adam

I have been following this build with interest. Would it be possible for you to give a Current Summary of all the features your ESC has to date in simple terms so even I can understand them? Where are you with the price as well.

Thanks Adam

George
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Old Jun 23, 2013, 08:44 PM
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Mesa Falcon Fld, Arizona, United States
Joined Sep 2004
426 Posts
George,

Thanks for your interest, here are the current features per your request:
*Brushed Motor Controller providing control in both the Forward and Reverse directions
*1.8A rated current (3.5A burst)
*1s and 2s lipo battery rated (device should operate up to 11V, but Low Voltage Detection most likely will not function as desired)
*Low Voltage Cutoff for both 1s and 2s operation - Device reduces throttle to half of the commanded position.
*Overcurrent Protection - Device will momentarily shut down the power till the over current condition has been cleared.
*Over Temperature Protection - Device will momentarily shut down till the over temperature condition has been cleared.
*Start up Throttle Safety - Device will not arm till it has been brought to neutral throttle.
*Small Size - Device has a footprint of .25" x .6"
*Software Upgradable - For those with a Microchip programmer, they can receive software updates and upgrade the device. For that matter, the user can create their own custom firmware, if desired, from scratch. (I do not expect that there will be many with the tools to do this; this is somewhat of an advanced operation. I have brought out the programming pins to very tiny pads that can be used to reprogram the device if desired)

The cost is looking to be between $12-15 US each device. Most of this will depend on the initial order and the price break that I can get on components.

Adam
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