Drill Motor/Speed Controller/Who Knows What Issues

[GMitchell]

Well, my team's cruising right along - at least, we're going faster than we did last year. Unfortunately, we've run unto a bit of stumbling block in the shape our drive train. Currently, we have the two brand spankin' new drill motors driving a pair of wheels. The wheels have sprockets on the outside to link to the other wheels. This is not the problem. The problem is that after only a brief moment of movement, the motors will stop dead. Not only that, but the lights on the speed controllers will turn a dull, milky color, rather like that of a dead man's skin.

This is a problem, to say the least. We are currently using last year's RC because of a minor screwup a week or so ago (how long does it take for FIRST to replace a fuse holder on the robot controllers anyway?), but that worked fine last year, so I somehow doubt that is the problem. Both the drill motors are in low gear, the program is as simple as can be, and everybody on the team is completely stumped.

Anybody have anything resembling an idea?

[com]

This sounds like an interesting problem.

The first thing I would do above all is check the current draw through the two drill motors, this could be the problem. Its possible something is causing the motors to stall out and draw tones of current making the speed controllers light go dim.

When solving any problem you should make a list of all the possible problems starting with the simplest down to the more complex.

Ex:
#1 Check for a short circuit.
#2 Check all wiring, possibly rewiring the robot.
#3 Try differnet motors for testing reasons
#4 Check speed controllers
#5 test outputs to the speed controlers

I think you get the idea,
It really sounds like there is a short circuit on the other side of the speed controllers between the motor wiring and the speed controller.

[Rickertsen2]

i don't know if this helps but red LEDs turn that color when too much voltage is applied to them.

[Randy_VanW.]

the same thing happend to us but it stopped I believe that it may be the lack of the 40 A circuit breakers? I guess we will just have to find out when we get them. (After all it is made to be hooked up like that.)

[Al Skierkiewicz]

Originally posted by GMitchell
The problem is that after only a brief moment of movement, the motors will stop dead. Not only that, but the lights on the speed controllers will turn a dull, milky color, rather like that of a dead man's skin.

Are you hearing any buzzing noise while this condition is taking place? That would be an indication that the circuit breakers are rapidly resetting due to the high current temperature inside the breaker. In a case like this, the first thing to do is raise the robot off the floor and see if it drives normally and all electrical is OK. If that works check for loose wiring on the supply side of the speed controllers. If all looks OK then watch the low battery light on the operator interface to see if you are drawing so much current that the robot side is resetting. Multi motor, linked drive systems are notorious for high current draws, use an amp probe to find out how much current is actually being drawn by each speed controller.
Let us know what you find.

[GMitchell]

Well, there is a slight buzzing noise, but it sounds (to my uneducated ears) more like a motor trying to run without enough power being applied to actually make it go anywhere.

The 40A fuses don't seem to fix the problem completely, though subjective observation makes us believe that they improve the situation somewhat.

As to current draw and resetting, our multimeter seems determined not to measure anything other than voltage, and it only cooperates with that sporadically. We have checked the wiring repeatedly and none of us can see anything wrong.

As to the 'low battery' light, that springs on at 12V and stays on, regardless of whether there is any active power draw beyond the LEDs. If the robot is pinned in place, the indicators on the OI will drop to 9.x while the robot is still straining, and spring back up to 12.x whenever the robot is released.

As to wiring other motors into the system, that isn't quite feasible - we've got FIRST's gearboxes for the drill motors driving the wheels, and substituting other motors into the system would probably be more trouble than it would be worth for the purpose of gathering information.

[Adrian Wong]

We have a similar problem; I'm not sure if it is related.

When I push the joystick forward with any amount of speed, the Speed Controller begins to blink orange and the motor just turns in 2 degree increments with pauses.

However, if I ease the joystick forward, I can get to full speed without any problems. It is only when I push the joystick with moderate speed that the situation arises.

[Thunder360]

I had a slight problem, but I went through and did a simpe easy check.

#1. Try a new fully charged battery

#2. CHeck relays they are easy to break

#3. Make sure your using the correct rely, this year and last years relys are a lil differant.

#4. Check to make sure that there is no strain on the motor that might pull it out of center, in other word check for tire wobble

#5. Check fuses and Breakers, no need to get this far and not chech those

#6. Check for any and all drops in Voltage, Amperage, or excesive Ohms

#7. if you've gotten this far its gotta be in the motors , I would have to say that the brushs might have some metal flakes in them, thats a comon problem for some motors, so try to blow it out with compressed air, but dont alow the armature to spinn as you clean it!

Hope this helps It may not but ohh well I tried. Also it really helps if you can test all of your parts individualy to test what works and what doesnt. Many thing can go wrong in a system, but a part by itself will either work, or die.

[rbayer]

What gear ratio are you running and what size tires? Also, what gear are the drills in?

[ngreen]

Make sure it isn't the joystick. We had one joystick that would center but wouldn't stay calibrated. The motor would buzz because of this. It worked perfectly with the other joystick. Good Luck!

[ryan_f]

aren't the 883's 60a continuous?

[Moshingkow]

This is a problem with the High gear on the drill motors. The same thing happens to us, but not in low gear.

Try setting your drill motor tranny to the low gear setting. Im not sure if its up or down, but there is a ring which slides on the drill motor transmission. Try adjusting that (not while moving!!!) it either has to be all the way up, or all the way down. if its in the middle, the motor will just spin.

When the motor is in high gear, it probably doesnt have enough torque to get the whole bot moving, so it is running at stall current (it draws the most current). This makes the breakers trip, and eventually, if you keep trying to move the motors, they will burn out.

You can verify this by listening for a clicking noise when this happens. That is the auto-resetting breakers tripping, then resetting.

The 40a breakers will help a bit, but im not sure because we havent gotten ours yet. Try some cooling spray if you really want to get that 29 ft/sec from the high gear setting! (but be carefull, the drill motors get REALLY hot, you may get a nasty burn)

TenkaI

[Al Skierkiewicz]

Originally posted by GMitchell

As to the 'low battery' light, that springs on at 12V and stays on, regardless of whether there is any active power draw beyond the LEDs. If the robot is pinned in place, the indicators on the OI will drop to 9.x while the robot is still straining, and spring back up to 12.x whenever the robot is released.

On the operator Interface there is a "low battery" light in the center section of the box. Does this indicator come on at all? It is an indication that the power to the controller has fallen below 8 volts. It may not be long enough to reset but it certainly indicates you are drawing high current.
To measure motor current you need an "AMP Probe" or similar high current accessory for your meter. Even a Fluke 77 can only measure 10 amps and you have to open the circuit to do that.
It still sounds like a flaky connection in the 12 volt wiring. This can be either the positive or negative side of the battery wiring. Are you using the maxi block and if so do you have a good connection to the metal plate that is common to all the contacts? Pull on all crimp contacts to make sure the connector and the crimp are tight. I know this is redundant, but check the wiring to the speed controller power input to insure you are connected correctly and the screws are tight and nothing is touching. Finally, check the wiring to the motor and be sure there are no shorts or dropped hardware. If you can post a pic so we can get an idea of the wiring.