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View Full Version : Electrical basics--need HELP!



mannyr7
05-30-2009, 11:01 PM
I'm having trouble wiring my Trendnet IP cam into Clyde.

I have two ancient 7.2V 1500mAh NiCad packs wired parallel to provide power to SSC32 logic, 7 Hitec 645Mg servos, 4 Hitec 5990Tg servos, and 2 Mato Toys airsoft cannon and a target board/Zigbee. I have a Maxx Products 6V regulator coming off the packs to the VL (35 mA) and VS (max 1 amp per servo?) of the SSC. The two gun motors in parallel do well at 7.2V unregulated (unknown amperage). The IP cam needs 5V at 2.5Amp but is coming up short. I have Dimension Engineering 5V reg for the cam and 3.3V reg for the target board.

I have the voltages all regulated properly, so my question is, how do I calculate the amp draw for all this?

Does every device need to be regulated somehow or will they draw the amps needed and no more?

BTW, I was planning on upgrading the battery packs to a pair of 7.2V 4500mAh NiMH packs. Will this be enough?

All available space I have for batteries is 2 standard R/C type packs. Maybe some 9V alkalines here and there would fit, if necessary.

All help and any suggestions would be greatly appreciated!

DresnerRobotics
05-31-2009, 12:40 AM
Devices will draw as much current as they need, no super easy way to measure exactly how much it's going to draw given that servos are going to fluctuate a lot.

What is likely happening is that it is pulling a decent amount and your old NiCads are having issues keeping up, and thus the voltage is dropping and killing your 5v reg line.

Two 7.2v 4500s on a BRAT is a bit overkill imo, you might see how a single one works for you. Remember, we only need 15-20 minutes of runtime on these. You have almost as much wattage onboard with two 4500s as my RX-64 mech... I suspect your problem is your insufficient batteries.

robologist
05-31-2009, 03:49 AM
The SSC32 appears to have 6 volts as a borderline voltage for VL, by point 4 here (http://www.lynxmotion.com/images/html/build136.htm).
Also, the camera pulling 2.5 A seems a bit much, but if so, the 5 volt Dimension Engineering reg used is only good for 1 A, might need to parallel a couple. Would be good to know what actual current draw for the camera and the Mato guns are, sometimes little motors can draw a lot. The HiTec 5990Tg (http://servocity.com/html/hsr-5990tg_servo.html)servos show a possible 4.2 A draw, not sure what the HS-645 (http://servocity.com/html/hs-645mg_ultra_torque.html) will do.

DresnerRobotics
05-31-2009, 08:54 AM
Actually that camera should only draw about 500mA at most.

jes1510
05-31-2009, 11:26 AM
That cam draws around 750mA when the wireless is transmitting. A 1A reg is cutting it pretty close though. I used a Castle Creations BEC since they come programmed out of the box to run at 5.1v and are good for 10A. The logic supply for the SSC32 and the target board can both run off of the BEC as well.

My tank guns peaked around 3A when starting up and leveled to under an amp when running.

You're fitting all that on a Brat? Impressive.