Prop resetting while driving Boe-Bot

Martin Hebel

Hi, using the Protoboard, trying to drive the Boe-Bot, but the propeller keeps resetting.· I added an extra 3300uF across 5V & Vss, but still occuring on fast speed changes.· Thoughts? Is this common?

Thanks,
Martin
·

Mike Green

I have a Propeller BoeBot using the Protoboard and its Accessory Kit. I've not had problems with the Propeller resetting. Perhaps the difference is that I'm using 5 AA 2300mAh NiMH cells for the power supply. I've got the regular 4 cell holder and an additional single AA holder glued just over the pivot ball and wired in series with the 4 cell holder. If you have only 4 rechargable cells, that's at best a 4.8V power supply. The 5V regulator isn't regulating at that sort of input voltage. It wouldn't take much of a voltage sag to lose regulation in the 3.3V regulator as well.

I'd also recommend putting a 1K resistor between the Propeller I/O pin controlling the servos and the servo control lead. This will help suppress noise from the servos.

Martin Hebel

Thanks Mike, actually testing off wall-wart right now. Maybe batteries would have better surge current?

-Martin

Beau Schwabe

Martin Hebel,

In addition to the cap, try a series diode to buffer the power to the Propeller. You may find you can lower the cap value as well when you do this.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Martin Hebel

Thanks Beau, seems much better with batteries, perhaps less noise. If I tell others to build this, what's your best recommendation for a schematic for a wide audience? Have others had the reset problem with the Protoboard? I searched but didn't find anything.

-Martin

Beau Schwabe

Martin Hebel,

This is a typical problem, but not isolated to any parallax product. Any time you have a processor and motors, and one power supply you will need to plan around any transient power fluctuations. Think of prosthetic arms or hands. There are several filtering techniques that you can apply that will contribute to a cleaner power supply to the processor which in any case will be the weakest link. A diode capacitor is cheap and effective for supplies that "dip" for considerable lengths of time such as a motor stalling, starting up, changing direction. A series inductor is good for very quick transient spikes... noise that could be caused from the brushes of a motor. A parallel capacitor also is good for quick transient spikes, but if the power supply is inadequate, it too will cause the power to "sag" if the load demand is too great.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Martin Hebel

Yup, understand the issues, so it's been a problem with the protoboard and I need not worry about it for others, or recommend which?

Martin Hebel

I'm also having issues with the PING locking up a cog occasionally using the ping Object. [noparse]:([/noparse]

Beau Schwabe

Martin Hebel,

It's not a problem with the protoboard specifically; it's an inherent problem with any setup using a single power supply.

It really depends on how well your power supply can deliver and maintain a voltage... batteries are usually better at keeping the voltage stable where as a power supply might dip more under a load, and that depends largely on the type of power supply. The motors also are a big deal, how much current are they demanding? All this needs to be considered.

Since you are also having ping issues, I'm still going to lean more toward this being a power supply issue. Have you tried using two power supplies? (<- with common grounds) Have you tried a series diode in addition to your capacitor?

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

SRLM

I'd second the power supplies. Today I was working on my robot, and hooked two RC car batteries together in parallel for the first time today. With just a small amount of forward movement it hit a wall and then went dead. I found that I had blown my 10 amp fuse. When I had just one battery, the robot could sit nudging against the wall all day without a blown fuse. I've concluded that previously in that case the battery could only supply <10amps and keep the voltage level. Now, I've replaced the fuse with a 15 amp. Hopefully that will help.

Martin Hebel

Ok, fixed the PING issue, forgot the 5V I/O to prop resistor. ** slaps head **

But really, how hard can this be to get a good solution? It's the protoboard and the Boe-bot chassis. There must be many using this combination including Andy. Sure, I've got an added 50mA cyclic load, but still... lol.

I've put resistors in all the signal lines. Still tends to reset frequently.

I'll try a second battery back for the Servo and figure out where to tap into.

Thanks,
-Martin

SRLM

Another thing is that the prop plug issue may cause resets. See this thread http://forums.parallax.com/showthread.php?p=790298 (specifically phil's response)

I was having that problem earlier tonight, but I stuck two 2k resistors from p31 and p30 to VDD. Cleaned things right up.

J. A. Streich

I had the brown out problem running off the BOE batteries too. What was happening for me is that the draw of the servos pulled too much power from the prop when using just the 4 double A batteries. The result was the prop would constantly reset every time the servos tried to move. If you do this draw your servo power from the 5v not the raw 9v or the life of the servos will be diminished. My solution was to run off 9v batteries. I have a thread on the issue, and I know I've seen at least one more; perhaps this is something we need to put in a gotcha's type thing.

What is the voltage and amperage of your wallwart?

Martin Hebel

J.A.,
Thanks, running with 2 sets of batteries. While not the best solution, seems to be working fine. The bot's going to be a major power sucker in any case.

Appreciate it,
Martin