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Old Jul 25, 2014, 06:43 PM
Dinghy's Avatar
United States, OR, Springfield
Joined Dec 2013
124 Posts
Help, 1S Brushed motor ESC 3+amp

I am trying to DIY replacement RX/ESC/Servos, for the HZ-PZ Ultra Micro bricks.

$60 to replace one of these bricks, Champ, UM T-28, P-51...etc ..
Dont really need stabilazition.

Goal ; Make a reliable Champ brick replacement for < half the cost of replacement.
Want to keep it light as possible, for indoor ultra micros, and foamy scratchbuilds,
using the available 8.4mm brushed 1S motors. (new version from Micro Motor Warehouse, look very good)

Lots of research/study, led me to the Lemon 6c RX Featherlite. $5.75.
HK 5320 and 5330 servos < $4 each.
....Thought the HK BR3A ESC would be the final major piece...
Ordered 2.....

Bench test seemed good, RX bound to my TX, Servos moved like they should, PZ P-51 8mm motor ran (no prop installed, so kept throttle at minimun)

Installed in my Champ with a dead $$$ brick.
Before closing up the fuse, gave it final trial run with prop.......
Before getting to half throttle, motor quit.. repeat...same.... tried 1/4 throttle, ran some for about 5-10 seconds then motor quit again.

Nutshell-----tried many batteries, different TX, 2nd RX, 2nd BR3A ESC, and a 2nd brand new never flown motor........all same failure.
Stronger/larger 1S lipos would run into a little higher throttle setting, but still failed before getting to 1/2 throttle.
Put a servo on the RX's throttle channel and that channel drove the servo as it should.

Tested Voltage output from the HK-BR3A ESC and found the voltage went from 0 to 4.11vdc (batt charge state) in the first 1/8-1/4 throttle setting.
Tested same output on a working Champ brick and found the voltage followed the throttle setting from 0 to only reach max voltage at full throttle.
These tests were performed, no load, motor disconnected.

You can follow my posts on this thread, pages 4 and 5, to get the full evolution of my trouble shooting.

Some have suggested trying to build a useable 1S brushed ESC from a servo control board.
Looks easy enough, if I can find the correct Resistors.

However some have said that solution may not provide the reliability necessary for safety flying indoors.

One opinion from postor 'Ruzam' sums up the weaknesses of servo board ESC's
" I've converted dozens of servo boards into ESCs for my blimps (I need a reversible ESC). It's easy and it does work. Some servo boards can handle more power than others (and it doesn't seem to be directly related to the size of the servo or the motor inside).


They have a very narrow dead band, and it changes with cell voltage and board temperature. So 'zero' throttle when you plug the battery in may not be 'zero' throttle when the battery runs down a little (you could even end up with reverse motor running at zero throttle). Second they have very non-linear response. You'll need to program lots of expo into your transmitter to get anything close to a smooth throttle response. I suppose it's better than nothing, but if I didn't need reverse, there's no way I'd continue using them.

Even more surprising, servo boards tend to be stupid heavy compared to an equivalent ESC.

If the stock bricks in these planes, like the HZ Champ, can accomplish a reliable 1S ESC function on a combo, all-in one, board,
there has to be a stand alone ESC solution that could duplicate this for a reasonable price and weight.

Any ideas ?

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Last edited by Dinghy; Jul 25, 2014 at 07:35 PM. Reason: add link to HK-BR3A ESC
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