Spare ESC for use at the champs?

[Ellis]

Hi guys. I don't like having to do this, but it's worth finding out what our options are.

We're running an Electronize 30a on our lifter at the moment, and electrically it's fine, but the relay-based control is really screwy. It's almost impossible to get the forks to sit flat on the floor on first try. We had hoped to get the thing working like a servo before the time, but it looks unlikely - we have to leave here in 10 days.

My question is whether anyone has a suitable ESC going spare that we may be able to use at the champs. Preferably a tz85, as we know they're up to it and I imagine the breaking function will help this over-shooting issue with the forks. Open to suggestions, though. The motor is rated at around 65a at absolute stall, if that helps you judge.

Obviously we recognise it would be a risk on your part putting your ESC into combat, so we'd work out a deal (I don't expect this for nothing, if anyone even has something suitable) and if anything in the slightest goes wrong with the ESC whilst it's in our hands, we'll cover the costs.

Thanks. Again, just investigating our options.

[grant_ploughbot]

Re: Spare ESC for use at the champs?

Are you using limit switches to stop at the top and bottom of the stroke? Or even just at the bottom?
I am trying to make up a small pic based limit stops for predator and my axe at the moment that can go straight inline with the RX/ESC so that you can use botbitz controller's etc without external relays and still get limit's. I might have one made up spare for the champs if you wanted to try it and see if it helps.

[Ellis]

Re: Spare ESC for use at the champs?

I'm open to try any setup. The problem isn't the travel limits though, as the weapon works like Sewer Snake's, and it goes underneath the robot as well as lifts up like typical forks (a lá Panic Attack). The problem is that the fork tips flat on the floor isn't an end of travel point (so it can't be limit switched or we'll effectively lose half of our weapon), it's right in the middle of the weapon's stroke.

Hard to explain...

I need to be able to stop the weapon when it's flat on the floor more easily, without it going past the point and lifting our wheels up or staying up a bit so it can't get underneath stuff.

I had hoped to make it work like a servo, so that TDC is the forks with 0 clearence, and it automatically reverts to that position after I use it, but having it work like a massive servo in ten days is looking doubtful.

You can see the problem clearly in this video:
http://www.youtube.com/watch?v=i8Lt-KWjs4Q

[Anttazz]

Re: Spare ESC for use at the champs?

Is there some way that you can set that as a default position? As in, when you release the stick it returns to a preset place.

[Ellis]

Re: Spare ESC for use at the champs?

Is there some way that you can set that as a default position? As in, when you release the stick it returns to a preset place.

Yes, servo control.

That would be the perfect situation, but even if someone has the right electrical side, it can't be plug-and-play, because you need to setup a potentiometer, which isn't all that straightforward in our machine unfortunately.

[typhoon_driver]

Re: Spare ESC for use at the champs?

Well if you cover the cost I could reprogram a turnigy 85a for you and hand it to you at the champs.

[PJ-27]

Re: Spare ESC for use at the champs?

Sewer Snake just uses it's and the forks weight to get them flat on the floor, he just slams them down and drives. No limit switches, no torque control.

I guess because of your lesser weight you aren't getting that?

What voltage are you running 5S?

[Ellis]

Re: Spare ESC for use at the champs?

Yeah, the weight of his forks brings them down, but we're using a higher reduction and in proportion less weight in the forks than he is, so it has to be brought down under power.

And yes, 5s.

Gary we may well take you up on that, I'll PM you if we do. Thanks.

[Eventorizon]

Re: Spare ESC for use at the champs?

We have 2 hacked TZ85A's that are spares for both Conker and Binky if you get desperate.

I also have two constant rotation potentiometers that I bought for my final year project but are now redundant. Designed for high stress applications it would be ideal for getting your forks working as a servo.

[Ellis]

Re: Spare ESC for use at the champs?

We have 2 hacked TZ85A's that are spares for both Conker and Binky if you get desperate.

I also have two constant rotation potentiometers that I bought for my final year project but are now redundant. Designed for high stress applications it would be ideal for getting your forks working as a servo.

Interesting! How would that work in our setup? Does it go between the motor and ESC or the ESC and Rx?

[Eventorizon]

Re: Spare ESC for use at the champs?

Bit more complicated than that but still fairly simple.

You would need some kind of microprocessor, an Arduino would be perfect. You attach the Pot to the main shaft of the forks, either directly or by a timing belt. The belt would probably be better.

This then reads the position of the forks in real time and sends it to the Arduino. The pot has 1024 position in a full rotation so your forks will be accurate to 0.35 degrees!

Your position on the transmitter comes out the receiver and goes into the Arduino. It them compares the position on the TX to that of the Pot. If they don't match it sends a signal out to the Forks ESC which then makes adjustments until the two match.

The Arduino can process at up to 115200 cycles per second so the delay between the two would be so small that you would never spot it.

With this and the help of another pot you can set the centre on the transmitter, trim the pot with another micro-pot until the forks are flat on the ground and then off you go :-)

[Ellis]

Re: Spare ESC for use at the champs?

Haha, well somehow I don't think that's going to be feasible on the morning of the champs. It's something we have to understand before being able to do it, which can't be good in such a small timeframe. Plus setting up a pot to work on the shaft isn't going to be straightforward. I'd love to say it's a goer but I don't see how, we have no workshop access between when we leave and the champs.

Hmm.

I'm up for doing any testing stuff at Yeovil or Colchester, the other two events we'll be attending this time. Bit reluctant to try anything completely untested at the champs in case it costs us.

[Eventorizon]

Re: Spare ESC for use at the champs?

I was never expecting it to be done on the day!
You would need access to a workshop, all the parts and even then it might take you two full days to iron out all the kinks.
If you are still around on the Sunday of the champs, I think we are going to stay and watch it all this year, I can walk you through it and explain what you would need to do to get it working.
If you are staying on for Yoville then maybe you could come to UWE and we could make a start there if I have enough time.

[RogueTwoRobots]

Re: Spare ESC for use at the champs?

Just to bombard you with options ( ) I've got two spare Victor 883s that I can bring along. Rated to 60A continuous and 120A bursts.

Had the same problem with Kaizer's forks a few years ago when using a 15A Electronize, always keep overshooting the ideal height. Switched to an 883 before the Edinburgh event and sorted it all out. Having the braking function makes an amazing difference.

I'll be there on the Friday so if you opt for it I can give it to you then, giving you the evening to get it set up (which is straightforward in itself). If it gets broken then it's not a huge problem as I need to send an 885 back to get repaired anyway.

[Ellis]

Re: Spare ESC for use at the champs?

Thanks! Do Victors have a breaking function, then? If so then that is a definite potential, as it *should* more or less behave like a tz85. We fight on the Friday, so it would need to be put in early that morning or if there's a rendezvous evening for the roboteers on the Thursday then that might be a potential. We'd need a deans on the in and out and then it could be plug and play in any case.

Won't say yes or no to anything quite yet, but thanks all for the offers and suggestions. Nice to know we have a fallback. Watch your inboxes.