anyone know how to use MOSFET's here?

[kchriste]

Neat robo-marionette you made there!

The best solution would be a switching regulator, but this would be too complicated at this stage due to your deadline. The easiest solution is then to add a battery pack for just the LM317/Motors that has a minimum voltage of +2.5 above the desired motor voltage of 3V. You'd need a battery pack that outputs more than 5.5V when it is at the end of it's discharge cycle. So, you'd need a 6 cell NiMh pack which has a nominal voltage of 7.2V for best efficiency with a LM317. If you changed the LM317s to an LDO, such as the AP1084, then you could get away with a 5 cell NiMh pack which has a nominal voltage of 6V but will be down to apx 5V at the end of its discharge cycle.

 

[electronicsfreak]

I only have 7cell NiMh battery packs that I'd be able to use. could I possibly use one for just the motors through the LM317's?

I know it would be less efficient, but it would still be more efficient than what it has set up right now and gives me more time to spend on the mechanical part of this (heh, it's still in pieces)

11.5W of power as heat per regulator instead of 20.7W

 

[kchriste]

Yup, the 7cell NiMh battery pack will be better than the 8 AA's wired for 12V. The voltage from them shouldn't sag as bad as the alkaline pack did either.

 

[ArtemisGoldfish]

Hm, did it HAVE to be powered by batteries though? : )

 

[electronicsfreak]

Hm, did it HAVE to be powered by batteries though? : )

to be self sustaining, yes.... if it wasn't then we probably wouldn't do very well next week......actually if we don't sucessfully complete the mechanical part of this then there is a pretty good chance that we won't do very well with this project at all.


it will be yet another animatronics project

 

[electronicsfreak]

Sorry guys for the extremely late reply on this, but here are the projects results
(after sorting out the programming issue at 3am) my group took first place at the competition with this.

There were no electrical failures, but a few mechanical failures (why I haven't posted a video of this thing) which will be sorted out before taking this thing to the national competition.

Thankyou all for your help with this...I could not have done it with out you.