Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: Trumpkin on January 19, 2008, 11:34:24 AM

Title: 7.2 volt battery
Post by: Trumpkin on January 19, 2008, 11:34:24 AM

I was wondering if the $50 robot microcontroller can run  on a 7.2 volt battery pack.

Title: Re: 7.2 volt battery
Post by: rgcustodio on January 19, 2008, 11:51:32 AM

the robot should be able to handle a 7.2 battery pack:
http://www.societyofrobots.com/schematics_powerregulation.shtml

the part used, KA7805ETU-ND, can handle a max Vin (input voltage) of 35VDC according to the data sheet (Absolute Maximum Ratings on page 2):
http://www.fairchildsemi.com/ds/KA/KA7805E.pdf

Title: Re: 7.2 volt battery
Post by: Trumpkin on January 19, 2008, 02:18:18 PM

thx!

Title: Re: 7.2 volt battery
Post by: Admin on January 25, 2008, 07:58:42 PM

servos cannot handle 7.2V, but the microcontroller with the 5V regulator can.

Title: Re: 7.2 volt battery
Post by: SkinnyDog on January 27, 2008, 11:24:55 AM

Hi guys

 Newbe here, i think i also went a bit over kill when i ordered my battery got a 7.2v 3000mah only realised the size when i got it, the connector plug?male pins is a lot bigger(thicker gauge wire) will have to down size it through the on/off switch.

This will work?

Electronics is foreign to me as i studied Mechanical Eng. im ok putting it all together if shown how but the calculations and terms are a bit of o struggle, i did manage to get my solar engine to work from my gunk bot book, it did take some time though.

Title: Re: 7.2 volt battery
Post by: gamefreak on January 27, 2008, 11:30:35 AM

the gauge is generally for the amount of current being drawn, more current lower gauge, thicker wire

Quote

(thicker gauge wire)

lower gauge is thicker, dont ask me why. so as long as you dont have the full 3 amps, you should be fine but if your thinner wires start smoking/melting/exploding then you may have a problem :P

Title: Re: 7.2 volt battery
Post by: frank26080115 on January 27, 2008, 11:50:52 AM

Quote from: Admin on January 25, 2008, 07:58:42 PM

servos cannot handle 7.2V, but the microcontroller with the 5V regulator can.

Servos can, and my servos haven't failed yet

Title: Re: 7.2 volt battery
Post by: SmAsH on January 27, 2008, 03:19:09 PM

yea i usually use 9V or 6V motors and then a 7.2V pack. it usually works for me :)

~smash

Title: Re: 7.2 volt battery
Post by: ed1380 on January 27, 2008, 04:06:59 PM

remember motors dont have electronics inside and they're ok with overvoltage, but servos arent

Title: Re: 7.2 volt battery
Post by: Trumpkin on January 27, 2008, 07:52:49 PM

yeah so basically i probably don't want to usea 7.2 volt battery with the $50 robot microcontroller. Just wondering cause I was planning on making a $50 robot microcontroller for some1 else and I had a 7.2 volt battery on hand. Couldn't I put a couple of diodes between the battery and microcontroller to reduce the voltage to 6v?

Title: Re: 7.2 volt battery
Post by: ed1380 on January 27, 2008, 07:58:38 PM

you mean resistors, right? cause diodes wont help.

resistors would turn that extra enery into heat. same thing the regular 5v regulator does. get a switching regulator

Title: Re: 7.2 volt battery
Post by: Admin on January 27, 2008, 08:00:11 PM

Quote

Couldn't I put a couple of diodes between the battery and microcontroller to reduce the voltage to 6v?

I think it will work . . . check the diode datasheet to make sure it can handle your required voltage/current/power requirements.

Title: Re: 7.2 volt battery
Post by: Trumpkin on January 27, 2008, 08:01:50 PM

Ok, i'll try that, thx!

Title: Re: 7.2 volt battery
Post by: airman00 on January 27, 2008, 08:19:35 PM

Quote from: ed1380 on January 27, 2008, 07:58:38 PM

you mean resistors, right? cause diodes wont help.

resistors would turn that extra enery into heat. same thing the regular 5v regulator does. get a switching regulator

true , but diodes have a voltage drop of about 1 V