Cheap Drive ESC

So I was doing some research whilst designing a beetle weight ESC when I came across these:
http://www.dx.com/p/jb-diy-10a-brush...3#.U6csjfldWSo

They're very cheap at about £5.50 each, and have free shipping to the UK. They only do 2 cell lipos, but at 10A with 20A peak they should do fine for beetle weight drive. The reviews look good as well. Has anyone else come across them previously? Seeing as I'll never beat them on price, I'm just gonna buy a pair of these instead of making my own for once :P

I'd be worried about a forward/reverse delay. Nice price though. The voltage is a massive limit, but I would wonder if they would handle 3s fine anyway, or maybe with a heatsink or something. Still got to be botbitz for me. £17 gets you a pair, but then you get a little stung on postage and the couple week wait. Very neat find though :)

I've seen those before on Ebay in 10 and 20a versions, the 20a ones state that they can handle 3s but then also have a voltage limit of 8.4v stated so who knows. They're a good price but you'll probably wait just as long for them as you would a set of Botbitz and for around £25 a set of Botbitz are cheap and you know they'll last.

Edit: Almost forgot here's the link for the 20a version in case you wanted to have a look http://www.ebay.co.uk/itm/RC-ESC-20A...item3f363a2e2a

All that being said, when Chinese or off brand stuff is good, its good. I have £10 escs working better than electronize ever did. Might get a pair of Rory's linked ones to see what they are like and if they can handle my abuses.

ive tried the 10a esc already there naff, the ones with a brake just stop if you try to go from full forward to revers until you center the stick and put it in reverse again and if you get the version without a brake and use a mixer it tends to twitch when your not touching the controls and 1 side will drive a bit faster than the other

also if you over volt them to a 3s lipo they get warm very quickly

I plan to get a pair some point soon, partly just to reverse engineer them to work out if they have any weak spots/ what their real specs are. If need be I may be able to just upgrade some components to improve the spec. Bear in mind that the featherweight ESC I made cost me ~£20 and locks up if you accelerate too fast, this is likely to be better than my thrown together homemade one would be on price, delivery time and quality.

The power wires on that 20A ones look a little on the thin side, those probably could do with upgrading a bit. The MOSFETS on it do at least look like they're up to the job. Might even be possible to up the current rating with a bit of hacking if required. Might have to get a pair of the 20A ones to replace the ESC in Richie if I can't fix the lock up issues; The difference between £13 and £25 for an ESC is substantial when the total budget for your robot is £100 :P

Edit:
Hmm, that sounds like current lockout.. what motors were you using with them?

i tried them on the usual BW motors

is it possible to remove a current lockout as i have some other esc with the same issue

The overcurrent lockout is a built in safety feature of a lot of motor driver chips; if the current spikes above the maximum, the chip will shut off all outputs until the chip is returned to brake mode (center stick). It's a really unhelpful feature when used in fighting robots; I had similar problems when designing my ant weight and feather weight ESCs. There's no way to remove it as far as i know unfortunately, other than to slowly ramp the stick from forward to reverse like I have to when driving my featherweight. There must be some solution though; my featherweight uses the same driver chips as the Scorpion XL ESC, which runs drill motors fine as far as I know...

The 20A one just uses 4 MOSFETs, which means it'll have none of the fancy safety features built in. They may have added extra circuitry to include it, but that should be easy enough to remove if necessary. I might get these for a beetle then, if the 10A ones are a little suspect...

lol i have 1 of the 20a 1s all bagged just gave it a quick test and they seem to work ok

but i would make sure it says the don't have a brake as i think you can get them with or without

These are the cheap 20A ones without brakes on the website i found: http://www.dx.com/p/jxh-xys-bl20a-20...8#.U6dNDvldWSo

Though I find a robot without ESC braking can be tricky to control, as it carries on moving when you release the sticks.

EDIT: Also, motor braking shouldn't affect that ESC, as it's way over rated for the a BW motor so should be able to handle any amount of stick waving, brakes or no.

well they seem to stop when you take your finger off the throttle but don't stop when you go from forward to reverse .... and they have the same sticker on as mine

All the brakes do is connect both motor outputs to 0v when at center stick. The motor'll stop at center stick with or without braking, but will be much harder to turn with braking. So when moving from forward to reverse quickly, the brakes will have little to no effect on the motor.

Didn't know Hobbyking did brushed ESCs... 30A continuous, 3 cell, under £5, UK stock, and good reviews... buying now!

http://www.hobbyking.co.uk/hobbyking...arehouse_.html

EDIT: Not buying now: no reverse :roll:

Hobbyking sell the F20A which has some code knocking about that will convert it into a brushed controller with instant reverse. They are also under a fiver. Trouble is it has the same mixing issue that some of the botbitz controllers have.

Couldn't find the F20A; this is the only other one I could see on HK.. http://www.hobbyking.com/hobbyking/s...=brushed%20esc. Seems alright, though it is only 2 cell. Also depends if it has full speed reverse...

I think I missed a dash. It's the f-20a. Here's the link.

http://www.hobbyking.com/hobbyking/s...dProduct=15202

If you look in the files section at the bottom of the page there is a guide on how to make it into a reversible brushed controller.

The F20A was the 25A ESC that BotBitz use to sell before it was replaced by the 30A ESC's.
The reason we abandoned the 25A ESC was the production quality changed dramatically and the controllers became rather unreliable.

Ok, so bought some of the 20A ones off ebay to run my featherweight, and they worked fine...

... after replacing the microcontroller with firmware that worked, upgrading (adding) the noise protection, and fitting heavier duty cables...

The firmware had a feature/bug which meant that you could go from forward to reverse just fine, but if you tried going from reverse to forwards, it would do nothing unless you held the stick centered for a second or so, and even then it only sometimes worked. It also didn't turn the motors fully on when the stick was at maximum throw. To fix it I modified the code used for my antweight ESCs, and carefully fly wired in the replacement microcontroller chip.

The cables were also pathetic, and got fairly warm even when running drill motors under no load, so I replaced them with cables of double the thickness. Also added an input capacitor which should have been fitted and wasn't, and beefed up some of the tracks to the MOSFETs which looked a bit weedy.

It's a classic case of the chinese reverse engineering a good design in the cheapest way possible; the circuit used is actually very good, but the implementation was lousy.

They now work pretty much perfectly, but were hardly plug and play! Still, not complaining too much; £13 for a featherweight ESC is fine by me :)

Firmware upgrade wired in (old chip shown next to the board)
Attachment 4698

Cable upgrade and noise suppression (bottom board is the original)
Attachment 4699


(These were the ones I bought: http://www.ebay.co.uk/itm/RC-ESC-20A...item3f363a2e2a )

What voltage would these work up to when modified?

Despite the fact they say 8.4v on the packet, I've run them up to 13V fine, and that was before all the mods. I went through checking the data sheets for every component I could, and none of them were rated for anything less than 20V, so I think they're fairly safe at 13V.

The board was surprisingly more robust than the spec said; the MOSFETS used could handle 32A continuous and 120A peak according to the data sheet. Normally with these things, they just take the specs straight from the data sheets. I think they must have toned them all down due to the lousey cables not being up to it...

The design was good enough at least that I may have to reverse engineer it for my heavyweight ESC..

wow ......if you get bored you could try getting these to work properly
http://www.ebay.co.uk/itm/320A-High-...item5d3bd80ccd

i got the first version which worked well and could happily run a 4wd bot over powered from 3s to 4s without getting hot but then they changed something and when you slam it from 1 direction to another they just stop

TBH, for £2 I'm impressed it did anything! That sounds like a firmware issue, so the same trick might work. Definitely have to check out those for my heavy! :L You able to get a detailed picture of the circuit board? Would give me an idea of the work required to upgrade it..

i did have 1 but cant find it will take a new pic and post it up tomorrow

Cheers :) What I really want to find out is what it's actual current rating is (put 320A through that and it will almost certainly explode spectacularly :P) and also if it can be run at / upgraded to 24v. I've spent £25 on my heavy so far, and the only part I'm lacking now is an ESC, so £16 wouldn't be bad if it could be made to work!

here are the pics hope they help

http://i1052.photobucket.com/albums/...ps76953a4e.jpg

http://i1052.photobucket.com/albums/...psf905373e.jpg

Thanks :) I can't read the chip numbers though; are you able to see what the numbers on the main drive MOSFETs are?

the nuber on the bank of 6 fets is

IRL 3803
R128p
U6 Z0

the chip on the bottom is
H1123 GB
LM339

Ah excellent, real chips! :P (International Rectifier and Texas Instruments instead of chinese brands). Both chips are rated to 30V, but the MOSFETS gate to source voltage is +/- 16v, which is where the 16V voltage rating probably comes from. If I just stick a 15V regulator on the logic circuits it should be fine at 24V :) I'll have to get on and purchase some; there's quite a good selection to choose from here: http://www.aliexpress.com/wholesale?...20140814095633

As I expected the 340A rating is made up from the MOSFET's peak value of 470A; the MOSFETS are only actually rated at 140A continuous, and looking at the photos it appears that the current goes through a single MOSFET on the high side, and two MOSFETS on the low side. Even the two low MOSFETs are only gonna be able to handle 280A, and even that's only a theoretical value. For comparison, the TZ85 speed controllers uses two 130A continuous MOSFETSs in parallel, and yet is given a realistic output current of 85A. Going on that theory, it gives our cheap '340A' amp ESC an actual current rating of more like 40A... still, not bad for less then £10!

It'll probably have some firmware issues, but the LM339 suggests that they're using the same type of circuit as the 20A one's I've used in Richie, which is a pretty workable design. It should just be a case of adding the 15V reg and maybe upgrading the firmware. The cables and smoothing look perfectly adequate for my motors (which only draw 5A! I'm hoping to upgrade at some point though..)

Cheers for the all the info :)

if you can mod them easily enough you should do a load and sell them the 1s running night fury held up to plenty of abuse

Id definitely buy a couple if they were modded to run at 24v and the annoying brake was removed

What was annoying about the brake? It'd be very easy to remove if I was replacing the firmware anyway, I just always have a brake on my ESCs otherwise I find steering my bots to be tricky... I'd have to buy some different PIC chips if I was gonna do firmware upgrades on them all, but that's not a huge issue, especially since it uses a 1mm pin pitch micro controller, unlike the 0.65mm pitch ones on the 20A board which are a pain to solder up...

Depending on whether I can do a decent mod to the boards, I could look into buying, modding and selling them... Gotta buy some for myself first :P

I didn't use them myself but from what I gather the escs would stop the motors completely when quickly changing direction

http://www.hobbyking.com/hobbyking/s...dProduct=46627

Very nice, but only good for 2 cell lipos :/

With the ESCs that folk were having problems with, when you change from forward to reverse, you couldn't just pull the stick from one end to the other. You'd have to centre the stick before attempting to reverse, aka full forward -> stop -> backwards. Not ideal for driving.

The other form of braking, which is the type I'm assuming Rory is talking about, is the one where, when you let go of the stick, the motors/wheels come to an abrupt stop, rather than coasting to a standstill. This type of braking is desirable in robot combat as it allows for more precise driving.

Yeah, the forward, stop, backwards one is almost unusable in combat, but I can see why they'd be great in an RC car say.
The brakes I implement are the ones where the motors are brought to a halt when you let go of the sticks.

2S in a beetle. I don't see the problem.

2S in a feather. Not for a pusher, but for a weapon with a drive, why not? 100W on 2S is only 16An and that's GR02 power.