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| S. Heslop:
--- Quote from: vtsteam on July 11, 2014, 07:48:02 AM ---Simon, question -- the battery on the servo tester in your circuit diagram -- does the ESC you purchased have an onboard BEC, and isn't the servo tester powered by that through the ESC connector? Could that be the cause of your short? If you use a separate battery for the servo tester, you may need to break the RCVR power connection from the ESC if it has an onboard BEC. Generally receiver power (~5V) is supplied through the red central wire in the ESC connector, and the central pin. The white or orange wire is usually the control signal, and the brown or black wire is generally the ground. --- End quote --- That could be it. I cant find anything that says it has onboard BEC, and the sheet that came with it is generic to a whole range of ESCs. But looking at that picture at the top of page 2, there is a group of 3 wires leading out of the ESC. I'd prefer to feed the servo tester with external power so I suppose i'll break that red wire. So far today i've been cable-tying stuff onto the half finished carry rack to have a go at testing the bike. But i'm still fussing about how to build a throttle. I'm not so sure if I want to be sitting on the thing trying to control the speed with a loose potentiometer. The pot inside of the servo tester reads 0-10kohm, so i'm gonna try using a 0-100kohm pot i've got since the throttle lever wont be able to go through the pot's full motion. Although I think I once read that potentiometers are often used instead of rheostats since they're kind of two-way. I just hope that using a higher value potentiometer won't muck up the servo tester's function. |
| vtsteam:
Check out the servo tester's function first with the original pot. Re. breaking the red (middle) wire in the 3 wire ESC lead -- you can do this non-destructively by pressing down with a paper clip wire on the square tab in the connector to release the pin and pulling the pin with attached wire out. ps. the BEC is the battery eliminator circuit. It is meant to output 5 V to the receiver to power it in an R/C vehicle using the same batteries that power the motor (usually much higher voltage). It is often powered by a linear voltage regulator like a 7805 IC. At least in cheaper versions. Usually the onboard microprocessor is programmed to cut the motor when battery voltage drops to a pre-set low, but to continue to supply the receiver with current through the BEC so a plane can be landed, even with the power off. ESC's vary in function. Most can be programmed for some of their functions. |
| John Rudd:
--- Quote from: vtsteam on July 11, 2014, 09:36:41 AM --- ESC's vary in function. Most can be programmed for some of their functions. --- End quote --- You will need to ensure that the brake facility is disabled........otherwise you might find the rear wheel will not freewheel...... :lol: |
| vtsteam:
True John! Though in my experience default is always brake off, out of the box. I also haven't found the brake to be very effective in real life with non-folding props. Slows them some, but it is far from a hard stop. Still, other features may need programming after trial. Timing for instance. Simon --bad timing is usually evidenced by a ugly sounding squeal on rapid throttle movement at low speed. Sounds mechanical like shot bearings, but isn't. Tipoff is that slow throttle advance (or smaller prop on a plane) doesn't cause the sound. Timing in that case usually can be altered by programming the ESC. |
| S. Heslop:
I'll have to read up on programming ESCs. I didn't even know that was a thing! It's been horrifically hot today, so i've tried stay out of the garage as much as possible. So I did a bit more electronics stuff. Soldering fiddly connectors and crimping terminals. Hopefully nothing will come loose and short out. I found when soldering DIN connectors (and wrecking two) for the commodore 64 that it's best to plug the plug into a socket to prevent the pins from moving when the plastic gets soft from the heat. I've got no idea on the 'polarity' of these meters but it wont be a hassle to switch the terminals if the needles move the wrong way. Maybe too much photos for such simple work, but I always get a little too excited about soldering. It's quite satisfying! Edit: Haha, aint that typical. I've been soldering all day without a problem, and then I give myself a nasty burn heating up one of those creme brulee puddings! |
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