Cheap Drive ESC

[Rapidrory]

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

[plargen]

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

[mrsam]

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

[Rapidrory]

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

[mrsam]

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

[maddox10]

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

[Rapidrory]

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

[RogueTwoRobots]

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.

[Rapidrory]

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.

[maddox10]

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.

[Rapidrory]

Bought these 2 ESCs (http://www.aliexpress.com/item/2x-RC...886703771.html) for £10 and have put them in a quickly thrown together Beetleweight entirely un-modded. They work a treat, although they don't have braking on center stick, but that's not too much of a problem..

10553900_10152443655076845_6966611735493323659_o.jpg

One of the modded pair of these that I'm running in my featherweight blew a MOSFET at the last event, but that was due to overheating as I just had it wrapped in heatshrink. I've replaced the blown FET and fitted some heat sinks and it's all working fine again

The pair of '340A' escs also arrived, but after detailed inspection it appears that they didn't have any proper gate driver circuitry, meaning that the MOSFETS are switching very inefficiently. I mean it worked, but it got warm just running small motors. There isn't much hope of running 40A through them for long that's for sure! I've started work designing my own Heavyweight ESCs now instead. They'll be largely based off a TZ85 just with different MOSFETS and without all the extra bits for brushless..

[RogueTwoRobots]

Nice to see some Cybot motors/gearboxes surfacing :P
Tried using four in a 3kg sumo bot a few years ago but they didn't quite make the grade.

[Rapidrory]

Yup They actually work pretty well as beetle drive units; speed is lacking on 2 cell, but they have pretty good grip and torque... and were free in my case which is the main reason why they were used :P

Yeah, they need heavily modding to use in anything with much more than a 3 amp draw; the ones doing the drive in my featherweight have been modified beyond recognition; the only thing that's original is the BEC system and the gate drive circuitry; everything else has been upgraded... still, cost less than buying proper ESCs and made for a fun project

[Craaig]

Cybot motors in a BW? Why did I not think of this. Hopefully my old Cybot stuff hasn't been thrown out, could make the next project a lot cheaper...

[Rapidrory]

Finally got around to testing one of my N2HV ESCs with beetleweight motors, and to my great surprise it actually works fairly well! It does lock up if it goes from forward to reverse too fast, but other than that it worked fine. I'll try and reduce the lockup effect further, but I make no guarantees..


Here's a video showing it working and the lock up effects: