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Brushless 1/32 Slot Car
#1

I’ve done some more on my ESC project for a brushless 1/32 slot car.
The commercial ESC I have, now has an ATmega 328 microcontroller, it came with an ATmega 8 so I replaced it for a decent spec variant. Writing code for brushless commutation is very challenging and interesting. 
I now have the ESC functioning fairly well on the bench, powering a Rockstar sensor-less 3500kv in-runner 2s (8.4v) motor. (From a mini z R/C car). 
I’ve also just purchased an outrunner 3/4s 2750 Kv, so it will be interesting to see how that works. I found an old worn out chassis to "experiment" with.

   

   
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#2

This looks a lot of fun - I’m following with great interest :)

c
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#3

Here's a comparison photo of a stock brushed slot car motor next to a couple of brushless motors. The Gold coloured motor on the left is an old drone motor that had a broken shaft. I borrowed one from a Scalextric F1 motor ( 1.5mm dia. ) to get the motor back to life. The Kv of  the Gold motor is way to high for slot cars imho so I'm going to rewind it and see what that does. The exisiting wire is approx 0.3mm, 6 turns x 2 strands per pole. I have about 6 of these gold motors so plenty of spares. 

The out-runner motor I recently purchased in the previous post was from a local "bricks and motar" FPV drone shop, interesting the business owner asked me if the motor was for "Scalextrics" and commented that he'd had a lot of people buying multiple motors looking for one that would work in slot cars.

   
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#4

Yeah, 7500KV may be a little too quick for a Carrera Bigsmile

...that's 90k at 12V Ambulance

Life is like a box of Slot cars... Cool Drinkingcheers
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#5

If you're looking for motor selection. Nobody sells more brushless motors than Hobby King. They start at $8, and have quite the range of windings.

Brace yourself for an eye opener.

https://hobbyking.com/en_us/power-system...ors&is_v=1
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#6

Just had to wait for some parts to arrive.
 I now have one the gold motors from the previous post rewound. The new wind is 24 turns per pole of 0.16mm single strand wire. ~1.7 ohms measured across the phase wires (original wind was 2 strands of 0.3mm x 6 turns per pole) 
First test on the bench sees the motor start easier and can run at lower rpm before stalling out. Runs nice and smooth also. 
I was quite surprised it ran first go, this is my first attempt at rewinding a motor.
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#7

Today I got the rewound motor mounted in an old car chassis, and got it running on the track. I changed the cars code to output a signal the esc was happy with.
Very drivable, lane changes, good acceleration. First laps @10V then 12V.
I'm using a stock Esc atm.

   
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#8

I'm still going on this :)
I rewound another gold motor and this time I tried 30 turns of the 0.16mm wire. It was fiddly but I got there in the end. The result however was that the windings are too bulky and I had to shim out the motor can to get enough clearance for it to spin. Anyway it works great on the bench and so I'll just use it to develop more esc code. As expected it's a little more docile than the previous motor I rewound with 24 turns, that motor continues to work nicely as well.

On the code side of things, I found the Blheli and SimonK project on git and all the source code is there for supported esc's. I've been reading the main asm file to gain insights as to better commutate bldc motors. There's lots of gold nuggets of info in there :)

Some AS5600 encoders have just arrived for some sensored experimentation. One would probably go well in a hand controller trigger?
   
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#9

PSA If anyone is using the As5600 module, the 10k pull down to gnd on the GPO pin has to be removed to get pwm or Analog from the out pin. 
I2C still works regardless.
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#10

Some more experimenting today with the stock ESC (Tower Pro Clone) with factory firmware.
One issue has been when traversing a lane-change the ESC stops and resets which takes a second or two, very annoying :) It's possible to drive fast and blip the throttle at the LC and the car continues but that's less than ideal imho.

So I tried putting a capacitor across the voltage sense pin as I thought the ESC is sensing low battery voltage and shutting down. Nope.

Next I put a diode (white arrow) in series with the voltage regulator that powers the microcontroller. It was placed in between track power-in (red arrow) and the input pin (yellow Arrow) of the regulator. I had to desolder the regulator input pin from the pcb and insulate it from the pcb with some kapton tape. The red and yellow wires that lead below go to a capacitor. 2200uf worked great on the bench, giving about 1 sec of power and the ESC not resetting with the 10v supply briefly interrupted. The idea here is to stop the motor from draining all the available power whilst the car traverses the unpowered part of the lane-changer.
   
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