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Reprogramming Brushless ESCs - Complete - No Support Offered
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marto
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Joined: 08 Jul 2004
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Location: Brisbane, QLD


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On bus so looking Todo list before controller is battle ready.

- PWM obviously.
- check fet switching routine - need someone who knows bit more bout this to help.
- failsafe
- test to failure

Other features which could be added
- status LED on unused motor bridge
- add exponential throttle curve
- tweak deadband and max/min rc values
- add interface to satRx - may have timer conflicts.
- add interface to br6000

For further development I need a selection of controllers to try and see what their limits are. If anyone wants to help out by donating some pm me. Otherwise I will buy some as I need them. The controllers Aaron suggested will be my starting point.
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Steven Martin
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Post Tue Feb 08, 2011 9:00 am 
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dyrodium
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Joined: 24 Aug 2004
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Actualy, I was going to suggest everyone should donate something, it's your time and effort that will have an impact on everyone in the sport! I'll be sending you some controllers with the antweight kit sometime next week. Smile
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Post Tue Feb 08, 2011 9:41 am 
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marto
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It would be nice but I am not going to stop development and hold people to ransom for donations. I think if I can get this going it might almost make featherweight kits feasible.

$50 drill
$80 for ESCs
$30 for lipoly
$30 for steel
$10 for wheels
$40 for receiver
$30 for charger
$10 misc wires and plugs

~$250 - $300 which I think is very reasonable price for feather started kit
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Steven Martin
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Post Tue Feb 08, 2011 10:44 am 
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Jaemus
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Hell yeah

I dont have anything useful to send to you but ill consider this next time im making a HK order
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Post Tue Feb 08, 2011 12:43 pm 
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marto
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Just bought 3x HK-10A works out @ $20.64 shipped for 1.5x antweight drives (If it works) Significantly cheaper than a B328 but will likely be bigger.

If anyone wants to send me 1 or 2 of these (list below). My policy will be modify, document and if it works you can get the controller posted back to you at your expense. If I blow it up or it can't be modified then bad luck but this would help with development.

Also I don't want 50 proven controllers to mod this is one time offer. If someone sends me a pair of controllers and you want the same ones done you can do it yourself or I may charge for the service if it isn't too much of a PITA.

HobbyKing 12A @ $7.81.

Beetleweights
TURNIGY Basic 18A @ $13.99
TURNIGY Basic 25A @ $15.86

Featherweights
Turnigy Brushless ESC 85A @ $36.59

Btw I leave for Japan in 2 weeks so might be a bit of a delay progress over that period.

Steve
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Post Tue Feb 08, 2011 1:27 pm 
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Knightrous
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Joined: 15 Jun 2004
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Location: NSW


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@Stevo: I can probably take on the task of programming controllers for people if necessary. Can leave you with the valuable time for developing more awesome Smile. I'm ordering the TZ85A's on Wednesday for this project, will probably do some destruction testing on them as well to see if we can get a roughly accurate rating on the controllers.

I also had an idea for a possible use for the 3rd half bridge, it could be used as a single direction, weapon switch. It would only need 1 wire added to the controller to provide the signal from the RX to the AVR. This could be used for powering small spinners (saws etc) or solenoids for flippers or even use it as a trigger for a relay/SSR.

Will talk more on MSN tonight.
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Post Tue Feb 08, 2011 3:27 pm 
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marto
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Indeed that is a very good idea. Also if you wire two controllers together. It could possibly form a 3rd H-bridge. Though PWM with this could get a little tricky and very easily result in magic smoke. If timings were very forgiving eg 1ms delays it could be used for direction control say on a drill lifter.

Actually, with two diodes and two Relays one half bridge could be used as a bi-directional weapon switch.

If you think even more creatively.... you could do a master PWM channel on the N fets and use the P fets to control relay directions and make one controller + 4 relays into a full bot control board. Although an extra controller at this point is prolly cheaper than 4 relays.

Excellent idea even more things to think about.

Steve
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Post Tue Feb 08, 2011 3:39 pm 
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Knightrous
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I'd also like to look into the possibility of current limiting (in a crude form at least). A bunch of these cheap controllers have ADC's checking the voltage inputs anyway, so it shouldnt be too hard to add it into software to work out the amperage draw based on voltage drop over a DC shunt. Could be another level of cheap protection.
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Post Tue Feb 08, 2011 3:54 pm 
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marto
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You have voltage points on the input voltage and on the motor wires. I wonder whether you could use the difference between the input voltage and the motor high side voltage to do some sort of current estimate. Might need to be empirically determined for each controller though.

Or I wonder whether you could measure the resistance of the motor using the ADCs then use an ADC like the open servo to measure the back emf. Then you could work out approximately how much current you might pull when you switched direction or when you switched on the motor.

First idea is probably more plausible than second.
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Post Tue Feb 08, 2011 6:13 pm 
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Knightrous
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Sounds interesting. Even if it's pretty rough, it might just be enough to stop it blowing up in a dead short or jammed gearbox scenario
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Post Tue Feb 08, 2011 6:23 pm 
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marto
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Hmmm maths time.

So in our circuit we have 3 "resistances"

rU - resistance upper bridge
rM - resistance motor
rL - resistance lower bridge

We have 3 Measure points

vB - voltage battery
vM1 - voltage motor 1
vM2 - voltage motor 2

I = v/r = vB / (rU+rM+rL)
I = (vM1 - vM2)/rM
I = vM2/rL

Hmmm dont think that helps unless we make some assumptions but we can get plenty of infomation

If we measure rU and rL then we should be able to get a pretty good estimate of current.
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Post Tue Feb 08, 2011 6:38 pm 
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marto
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Actually if we knew rU and rL then we can make two estimates of current and then average them. We could also calculate the resistance of rM based on the difference in vM1 and vM2 which could be used to detect short circuit.

Of course rU and rL are probably more like voltagedrop+resistance so may not work too well.

However could use points to measure voltage drop. Not sure how to measure resistance though. Other than with multimeter. Would be nice if it could be done automatically.
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Last edited by marto on Tue Feb 08, 2011 11:21 pm; edited 1 time in total

Post Tue Feb 08, 2011 6:43 pm 
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Valen
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get the data from the fet datasheet
note rdson will be fairly non linear with regards temp

is there no "mini" osmc?
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Post Tue Feb 08, 2011 6:53 pm 
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marto
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Indeed hadn't thought of that. Sort of screws everything. Really need a shunt resistor to measure accurately. However if you are measuring the voltage drop to gauge current if the resistance increases due to temp increase it will increase voltage drop hence overestimate current. This could be a good thing as it would regulate temp as well as current.

Anyway should prolly just see if it will work without any current limiting to start off with.
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Post Tue Feb 08, 2011 7:07 pm 
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marto
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In case anyones interested I just got PWM working.

Steve
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Post Tue Feb 08, 2011 10:13 pm 
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