Ever wonder what's inside the stock Voltage ESC?

[sadlerbw]

Bah! Foiled by ARRMA! Two problems trying to use a 3S lipo: first, the big capacitor on the ESC was indeed rated at 10v. That would have popped on a full 3S pack, so I desoldered it and found a 16v cap to put in its place. However, the control system must have some sort of over voltage protection because turning it on with a 3S made the status LED rapidly flash blue and it didn’t respond to any throttle inputs. It wasn’t that replacing the cap damaged anything either, because it still works just fine on 2S.

If I still want to keep trying, I’ll have to figure out how the brain is reading the voltage, and see if I can trick it into thinking the voltage is low enough to be safe. Not sure if I will take it that far or not. Depends on how much free time I can devote to playing around with it.

 

[GRspeed]

Rock on!

 

[GRspeed]

In so far as these things were dropped in conformal coating for waterproofness, both of my Voltage models demonstrated problems when wet. Both were also on standard servos cause the 5 wire crapped out on both of them. One of them had the original 5 wire rubber plug not seated and water entered the case. Dried it in rice and it worked fine after that but stayed finicky with exposure to moisture. Then the other began to do the same thing and that one finally stopped controlling the servo.

Now they are interesting looking paperweights.

 

[PowerDubs]

Unfortunately, almost everything in their datasheets is in Chinese, but there was a least a pin-out with some english on it.

You can download an app for your phone that you just point at the screen and it will show you the translation on the phone instantly. Easy peasy.

 

[sadlerbw]

I dug around and eventually found the english version of the manufacturers website. There wasn't a link to it from the Chinese site, and the name was almost the same, so I kept thinking it was the same place in the google search results! Once I figured that out, I was able to guess what the product number was and find a datasheet. Turns out the 'brain' is model HR8P506FHNK. It's a 32-bit chip with a single ARM processor core, 32K of Flash, and 8K of RAM. It has a bunch of outputs that can do PWM for controlling the MOSFETs and something like eight pins that you could hook up to it's analog-to-digital converter. One of those pins is almost certainly watching the battery voltage, but the package for this chip doesn't really leave the pins exposed, so I have to find something they connect to down-stream to probe in order to figure out what a given pin is doing. Also, the ADC can't read voltages above 5v at most, so whatever connection is watching the battery probably already has a voltage divider on it to step things down to a range that wont burn out the brain. If I find that voltage divider, maybe I can mess with it to make 3S possible.

As for still being able to kill these things with water, from what I saw the servo connectors are probably the most vulnerable part of the whole board. That is one place where you can easily get water shorting a signal line from the brain straight to ground or +5v. The other place, on mine anyway, that might have been vulnerable was the big electrolytic cap. The leads were MOSTLY protected, but there was still some wire exposed. Shorting across that cap wouldn't necessarily hurt the cap, but it would remove any protection from voltage spikes that you were getting from it. However, you would need to pretty much dunk the ESC in a puddle to get water in there. It was really only the 'tall' components on the board that weren't covered in silicone. I still think the servo plug is the most likely killer. If you wanted to protect that connection, just squirt some silicone caulk or gasket maker over it with the plug in place to seal things up. You can peel the silicone off easy enough if you ever need to get the wire unplugged, and silicone is pretty cheap. Once it is dry, it wont attract as much dirt as dielectric grease either. Those little rubber covers aren't as effective as a glob of caulk!

 

[sadlerbw]

Muahahahah! I found the voltage divider, and made myself a really fragile 3S ESC! I’ve got it hooked up to the stock 20T motor just sitting on the bench right now, but it does spin the motor and respond to the controls with a 3S battery plugged in! For anyone curious, the two original resistors were 47k-ohm and 10k-ohm. To scale it for 3S, I used a few resistors that added up to 15.5k-ohm, and then a single 2.2k-ohm.

There are a few problems with what I did though. First, it is super-fragile. The place where I need to connect the voltage divider back to the CPU is a teeny tiny little pad, and I just can’t get a solid connection to it with a piece of wire. Also, the resistors I used are all just hanging off in the air. They are all soldered together, but that still isn’t a durable solution. Second problem: I can’t use 2S anymore. My modification isn’t smart, so if you plug in a 2S, it just kicks in the low-voltage cutoff. Third, it won’t fit in the plastic case anymore. I didn’t have quite the right capacitors on hand to replace the original 10v one, so I just soldered on two smaller value ones, one on each side. That worked, but they are sticking out both sides of the board, and don’t lay flat.

But I don’t care about any of that. I just think it is cool that it can be done! Also, I finally got off my butt and grabbed some picture of the ESC’s circuit board. I had already removed the original capacitor at this point, but other than that it is stock. The first picture shows the two resistors that made up the original voltage divider. They are tiny! I also have a picture of my homemade voltage divider in the last pic. It is more proof-of-concept than ARRMA tough!