PSC and CMUCam Troubles

bigdom324

Hi everybody,
I built a robot with with a bs2sx and boe.· Currently, I have a a Ping sensor, PSC, Solarbotics motorcontroller, serial LCD, CMUcam app mod, PSC and PIR sensor connected to my robot.· I have the Ping sensor mounted to a servo and I also have a claw driven by a servo which· are both connected to the PSC.· I made a object avoiding program that worked pretty well using the Ping sensor and the homemade turret that it is mounted on.· I have also made programs for the CMUcam using the demo code that I got offline.· However, if I have the·CMUcam connected to the BOE at the same time as the PSC, the PSC will cease to function after a couple of seconds or not function at all.··Sometimes the green light will flash on the PSC, but it is obviously not working because I can't hear the servos being held at their neutral position.· I am almost positive that this·is a hardaware·issue because the PSC will power on for a piece of code that it will not power on for,·once the CMUcam is connected.· Maybe its because of the way the appmod is hooked up to the boe?· Anyhow, I am really frustrated with the situation and·I am hesitant to plug my servos directly into my boe because they will not have a seperate power source like they do with the PSC and I am getting a lot of flutter/lack of precision control.· I can't position the servos as well as I do with the PSC.· PLEASE HELP ME SOMEBODY!

Thanks for your help.

Mike Green

This sounds like a power overload. What's powered by what and what are the average and peak current loads of each device? Check particularly for the PSC and CMUcam. The regulator on the BOE is limited in what it can supply, usually 1A total current, and limited more by power dissipation. Any voltage over 5V will have to be dissipated as heat. What are you using for a power supply voltage? How hot is the regulator getting?

bigdom324

Hey Mike,
thanks for your reply. At this time I do not have a way to measure the average and peak current loads of each device, but it sounds like you are on to something; I hear that the CMUcam draws a lot of power.. The CMUcam, lcd, Ping sensor, PIR sensor are all run off of the regulated power of the BOE. The PSC is also plugged into x3 slot 13, however, it is powered by a 6 cell nicad battery that also powers the motor controller. Even if the PSC and the CMUcam are the only things plugged in, they do not function properly together. I have a 9v 300ma power supply that I bought from Parallax for my BOE and the regulator only gets slightly warm.

Mike Green

Look in the manual or datasheet for each device. You do need a rough power budget. The PING uses quite a bit of current for short periods of time. I'm sure the CMUcam can use a bit of current. Servos can draw over 1A each under mechanical load. I suspect your 300ma supply is "overdrawn at the bank" from time to time.

bigdom324

Good call Mike, my power supply was "overdrawn at the bank." I just purchased a 1A power supply this morning and everything seems to be working fine. I guess the ironic part is that when I bought everything last year, I purchased the 300mA charger over the 1A to save $1 because I didn't know how much current each compent drew. This morning I had to pay $18.99 at radioshack for this fancy variable voltage power supply. I guess you live and learn. Thanks again.

Mike Green

With a variable or adjustable voltage power supply, use a 6V or 7.5V setting rather than the 9V setting if you can. This will reduce the power dissipation of the 5V voltage regulator. What are you using to power the PSC and the servos?

bigdom324

Yea, I have my power supply voltage set to 6V for just such a reason. I have a 6 cell, 7.2V Nicd battery for my PSC and servos. However, it is not directly plugged into the PSC. I have a solarbotics L298 Motor drive kit which has a regulated 5V line out that I have connected to the PSC. This setup has been working well for me and I have enough power for my two GM8 motors and my servos. Nothing gets overly hot and I have decent battery life.