Printable View
Almost finished putting together a robot that's been in parts for many years. Just got the gears lining up correctly.
http://imgur.com/SeWs6cf
Having a little problem with the electronics which wasn't happening yesterday: when I power up the fuse for the right electronize blows. I cant see any shorts- any ideas what might be causing this?
Cheers,
James
Are you using an external BEC or RX battery?
No rx battery- so I guess yes to the BEC (sorry, I'd never heard that term before).
I meant an external BEC, the one on the Electronize looks like it's connected so if you were using an external one as well that could cause it to blow i believe.
I'm sorry- what is the BEC? The Rx is powered only by the electronize- I've not put anything else on to power the Rx.
Battery Eliminator Circuit
It supplies power to the receiver and nothing else
(Correct me if I'm wrong)
The orange and yellow intertwined wires are the BEC, this powersw the RX yes. I can't tell from the picture but you only need one of these connected, if both have them connected you will overpower the circuit, just cut one of them and tape the ends off
Exactly that John, it's the two wires (orange and red) that are twisted together, actually looking at your picture again are your rc wires plugged in correctly? the signal (white) should be on the front of the RX.
Only one of the electronizes has the BEC, and it isn't plugged into the Rx (is it meant to be? The Rx is still getting power).
I noticed that the red and orange wires are making contact- presumably this is not desirable?!?
The wires are supposed to be connected if you are using the BEC on the Electronize because that's the circuit, what i meant was other than the Electronize BEC are you using an alternative external BEC?
connected to each other? Yeah, as far as i know thats the only thing powering the rx- no batteries or anything else...
Are those 15A electronizes? And what are those motors? They looks quite powerful so could be easily drawing more than 15A so blowing the fuse. They may not have blown yesterday if the gears where not connected as this will add a lot of extra resistance so the current draw will be higher so the fuse will blow. What is the rating of the fuse?
20a on the fuse from what i can see, might be exactly what Max is saying and the motors are drawing too much current, it might be worth investing in some huger rated esc's.
the fuse blows as soon as the battery is connected. Before the motors even turn.
Fuses are 20A
motors are feather golds and i had one running under load yesterday. Like i say, now I cant get them to run with no load at all.
Should the orange and red wires go to the +ve and -ve of the receiver? Or to each other?
Thanks, James.
https://www.youtube.com/watch?v=f_Xo...ature=youtu.be
Got it working in the end. Just need to fix the wheels on a bit better now........
whoahahahaha, I think you might be right :D. Good speed though.
Looks great, nice speed and very compact. All i would say is protect the wheels if you can, they're food for an axe or spinner right now. Oh and fix them on properly. .....obviously.
Yeah, planning on having another layer of armour outside the wheels. Need to find out what weight I've got left to play with. There's no size limit on FWs is there?
From what I know there isn't. Only antweights and heavyweights are restricted within their dimensions
There is a size limit. to featherweights - it's the doorway...
Ah the good old days of wheels falling off. Used to happen to me all the time on my old wiper motor bot, and for the first wee while when I transitioned to drills. I kinda miss it; damn improved building techniques!
any tips on keeping them on then? ;)
Grub screws, circlips, collars/collets, nuts - whatever best suits the design and how the wheel is mounted etc :)
You might want to try adding a layer of armour to the outside as well as an outer bearing along with that - I think that might be very handy for this kind of design, and definitely will reduce the stress on the wheel axles I'd imagine. Would also help keep them on too!
Wheels sorted. Made it into a thwak bot for now (10kg before i added that).
Planning on making a range of (boring) weapons to be bolted on the front including a practical scoop. Not sure I can fit anything active into 3 kg.....
https://www.youtube.com/watch?v=-XAA...ature=youtu.be
Attachment 4723
Got problems charging. Using an Imax b6ac charger and a turnigy 3000mah 22.2v (6s) lipo.
Error message reads "low voltage".
Battery voltage is 14v on my multimeter. I'm worried I might have knackered some cells in there...
Obviously I now won't use it until I know what's going on. I'd it something stupid I'm doing wrong or is the battery done?
James.
If it's reading 14v it's severely discharged. Works out to 2.3v/cell assuming they're discharged evenly, which is a good way beyond what they should be. A high end charger might be able to resurrect it. Have you tried Charge or Storage instead of Balance? The Imax might happen to be okay with the lowlow voltage in other modes. It's very possible the pack is permanently damaged and trying to force charge into it could be dangerous, so I would put it outside and keep a very close eye if it does accept it. It might also be wildly unbalanced so only charge to say 3v per cell and then switch to balance.
Not very recommended but you might save it. Looks like overdischarge, easy enough to do but you won't do it again. :P
I'd suggest getting a LiPo alarm/voltage reader for a couple quid from Hobbyking. Allows you to stay on top of the voltage and stay above unsafe.
Yeah, tries the other modes with no luck. Don't think my charger up to the job.
To do what I did its it just a matter of running it until the battery is completely flat?
Seems likely, with LiPos you want to avoid going below about 20% capacity. Not sure what that equates to per cell, something like 3.2v. I'd keep the pack in a charging bag at all times until a solution can be found (a roboteer buddy with a high end charger maybe) - likely to be answers online about how to resurrect. Of course, be wary of anything outrageous, LiPos are sensitive beasts.
Sorry but that lipo will be dead, from memory 2.8v per cell is minimum capacity I have my cut off set at 3v per cell,
So 6x2.8v 16.8v .this is not always dangerous but it will have damaged the battery capacity and current draw. The chargers won't charge below set voltage points because if you charge the lipo it is likely it will puff and be potential dangerous, my advice bin it safely and get a cutoff unit or a buzzer alarm at least whilst testing,
Just to point out we drained one of Binky's 5S lipos down to around 2.2v-2.5v per cell in 2013. With the Big Nipper teams Pro-Cell charger it was recovered and has been functioning fine ever since.
The consensus used to be that dropping the voltage on a lipo used to be its death but now it seems with a few more years of testing that it is massive current draws that do permanent damage. It was hard to spot this as it usually took a high current discharge (expected or unexpected) to drop the cell voltage that low. (This info comes from one of the New Scientists magazines regarding electric vehicles that use Lipos while comparing them to lithium Ion)
Keep hold of it and wait until you are at an event where someone will let you use one of the top of the line chargers. It may be dead but I reckon it can be saved.
Yep, it was that pack, Alex, that I had in mind when saying a pro charger might be able to resurrect it. That and I accidentally ran my beetle's 3s down below our charger's threshold last year, and I forget how we did it (tricked the charger I think), but it restored fine and is now in the spinner. 2.2v per cell is extreme and may be beyond rescue but there's nothing wrong with trying to (safely) restore it.
As long as none of the cells have completely died, its possible to recover the battery by giving it a partial charge to bring the voltage up to a point where the Lipo charging program recognises the pack as having 6 cells. The best thing to use is a current limited bench power supply but as they are rare, you can use the Imax charger in it's Pb (lead-acid) mode.
* Set the charger to an 18V Pb battery and low charging current, 0.5A or less. Don't connect the balancing cable at this point. The charger should accept the pack as a
* When the charge current drops down to almost nothing or the charger finishes its cycle, the battery should be charged up to around 18V.
* Disconnect the battery and check the voltage. Wait around 15 minutes and check again; if the voltage is the same or only a little lower, the pack is savable, if the voltage is heading back to 14V, its dead.
* Assuming the pack holds its voltage, set the charger for a 24V PB battery and start charging again. You don't want to complete this charge cycle, you just need to raise the battery voltage to around 20V so that the lipo program recognises the pack. Charge for 15 minutes, check the battery voltage and repeat until the pack holds around 20 to 21V.
* Set the charger to the Lipo mode, connect the balance cable, set the current down low and try charging. If the charger still indicates low voltage, try more time on the Pb charge mode. If the charger accepts the pack, monitor the individual cells by pressing the DEC button (described on page 30 of the manual). If any of the cells are wildly different voltages, you probably need to switch over to balance charging.
To stay safe, do all this outside on a non-flammable surface. I have brought back several packs this way and while they may have balancing problems or a shorter life span, its worth trying.
Hi guys,
Tried what Nick suggested today, got the voltage up to 18v but wouldnt go any higher than that on Pb mode and wouldnt recognise the battery on LiPo mode... I'll try again tomorrow, failing that I might need to borrow a proper charger at the uk champs.
A 'proper' charger might not do any better - all Lipo chargers have safeguards to prevent you charging a pack to the wrong voltage. If your pack's voltage is still outside the range of a normal 6S pack, then all chargers should reject it. It could be that one cell has completely given up and you can test that by measuring the voltages on the balance cable.
There should be a black wire on one end of the balance cable and that is the negative connection. All the other balance wires go to the positive side of each cell and you can measure the voltage of each cell by placing one multimeter probe on the black balance wire and stepping the other probe along the connector. If all the cells are OK, the voltage will step up by about 3V as you measure across successive wires. If the voltage steps up significantly less than 3V at some point, that's a dead cell.
What I did to revive a recently over discharged pack was to partly charge it with a bench supply. I set the voltage to 22V and the current limit to .5A and got the pack voltage up to a point where the Lipo charger could balance the cells. The good thing about a bench supply is that it has no safeguards and just does what you tell it; as long as you treat the Lipo with respect and monitor its temperature, using a bench supply should be quite a safe way to revive a pack.
Btw, what's the bit in brackets in the title meant to mean