Problem With Servo Controller

John Burrow

I connected the power on my Servo Controller, turned On the switch on the servo controller, and killed a 4x20 LCD that was connected to the same 5v supply line. Another 4x20 LCD on the same 5v supply blanks out, but recovers (on system power off/power on).

There's nothing else connected to the Servo Controller, just the ground and the +5v. The 5v comes from a PC power supply, and reads exactly 5v on my meter.

Can anyone tell me what's going on? I'm about to use my sledgehammer on the Servo Controller....

Thanks,
John Burrow
San Diego

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SRLM

Are you resting your PSC on a conductive surface? I did something like that. I wasn't thinking, and mounted the PSC tight against an aluminum bracket. It short circuited (or something) and the chip got really hot just when plugged into USB. In short, try it again and hold it in the air.

John Burrow

SRLM,

Thanks for the suggestion.

The Servo Controller is mounted on standoffs above a non-metallic (essentially wood) surface. But I'll go try·your suggestion·anyway.

I measured the current flow on an old analog meter, and I see a 'kick' then it settles down to almost nothing.

Also, what would cause my LCD to burn out?

Thanks, John

Chris Savage

PC supplies are notoriously noisy and not recommended for microcontrollers without adequate filtering. If you look at a PC motherboard you’ll see several filtering circuits designed to filter the supply noise. The parts you connected don’t have this filtering and very well may have been damaged by that supply. The meter you connected won’t display noise, just average volage.

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Chris Savage
Parallax Engineering