Power Supply

[cwkoehler]

Hello,
I needed to know the maximum supply voltage for the barrel connector of the IsopodX. The wall transformer says 6VDC at 300mA. When I probe the inside and outside of the barrel connector with my volt meter I am reading between 11 and 12 volts. I am a little confused by this. What I would like to do is wire my own barrel connector to a DC supply using C-cell batteries yet do not have enough information to make an educted choice. The online manual seems to indicate 5.5v as the absolute maximum. Now I'm thoroghly confused. Any insight would be greatly appreciated. Thanks in advance.

cwkoehler

[RMDumse]

The AC to DC walwart we provide is under no load when you probe it with your meter. A better test would be to plug it in, and see what the voltage going to the board regulators were, with the IsoPodX taking around 200 mA.

I run my IsoPod(TM)s very successfully off of 4AA NiMH rechargables for a at least couple hours between charges. 4 C-cells ought to be just that much better, depending on their capacity.

The input on the IsoPodX for Vin is different than the 5V rail, however, the Vin feeds the 5V regulator, that then feeds the 3.3V regulator. There is nothing of significance (maybe the CAN bus driver chip on IsoPod(TM) but I don't think so on the IsoPodX, but I'm working from memory without schematics in front of me) running off the 5V on the board, but all the logic is at 3.3V.

[cwkoehler]

thanks for the prompt answer

[subot.robot]

Can I power the servopod from 7.2 volts 3.3A battery? Will the servopod get damaged if I connect external powersupply of higher voltage and current? I think all the power to chips comes through the output of voltage regulator. If yes, then does the maximum voltage that servopod can withstand depends on the maximum voltage the voltage regulator can withstand? Can anybody please explain regarding connecting the external batteries to servopod and the maximum voltage and current. Is the maximum voltage that can be fed to servopod is 5.5v?

regards
subot.robot

[RMDumse]

Yes, you can power the ServoPod (any of the Pods) from a 7.2 battery stack. Current of the pack doesn't matter as long as it can source at least the ~200mA's the board needs for the duration you'll be needing it to run. I've powered the boards off 4AA's (5-6V) and 7.2 packs (which can be as high as 8.4 freshly charged).

Yes, all the voltage goes through the regulators. So there is a cascading step from Vin to 5V and from 5V to 3.3V for the digital logic. The regulators are rated at a much higher voltage, but a higher source will mean the 5V regulator has to disapate too much heat. It may go into thermal shut down to protect itself (or worse). Usually above 9V the 5V regulator get to hot.

I don't understand that comment about 5.5V. 7V is a good target voltage to feed the Vin. The 5V rail (output of 5V regulator) can be supplied directly (bypassing Vin) but then it should not be above 5.5. Maybe that was the intent of the reference.

If you want to run from a higher supply with more efficiency, consider the SR option. This adds a switching regulator which switches down the supply voltage. In the process, you get a "transformer" like gain, and the actual current drain goes down. We chose the SR to work with typical automotive batteries. With a typical 12V battery, the SR version takes 100mA and generates very little heat.