Author Topic: 7805 and 7V2 NiMh  (Read 1844 times)

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Offline TrickyNekroTopic starter

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7805 and 7V2 NiMh
« on: February 10, 2008, 07:37:47 AM »
Good day everyone

I was just wantering if it's safe to use a 7.2V NiMh battery with a 7805...
7805 isn't a LDO, will this generate problems powering up my electronics???
My controller is a ATMEGA16 with brown-down at 2.7V running at 16MHz...
Some other electronics also have lower operating voltage than 5V
I also will be measuring the battery condition with a DS2438A (free sampled xexexexe x) )
And I'll be powering two servos (HS-311) directly from the battery...

To be clear of mind, I'm just asking if 7805 is a good solution for powering my electronics (I'm both bored to
get a bus to go downtown and have no time to go get a LM2940-5T which I usually use...)

Thanks in advance!!!
Lefteris, Greece
For whom the interrupts toll...


P.S. I've been inactive for almost a year... Don't give promises but I'll try to complete my tutorials. I'll let you know when..

Cheers!

Offline jsmoker

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Re: 7805 and 7V2 NiMh
« Reply #1 on: February 11, 2008, 06:37:18 AM »
I think you should be fine.  If I remember correctly, you don't see any effects with drop out until about 6.2-6.5 volts.  Even then, you only go down a little.  I think they're also rated for 1amp so as long as you don't have a large load on the servos, you should be fine.


Offline TrickyNekroTopic starter

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Re: 7805 and 7V2 NiMh
« Reply #2 on: February 11, 2008, 08:05:23 AM »
Nice! Thanks all I wanted. Thank you! :)
For whom the interrupts toll...


P.S. I've been inactive for almost a year... Don't give promises but I'll try to complete my tutorials. I'll let you know when..

Cheers!

Offline Admin

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Re: 7805 and 7V2 NiMh
« Reply #3 on: February 11, 2008, 02:55:21 PM »
Datasheets, dude :P

It will mention a dropout voltage . . .

Battery_voltage - dropout_voltage > minimum_microcontroller_voltage

So if say the dropout was 1.5V . . .

thats 7.2V - 1.5V = 5.7V . . . way above your brownout.

Offline TrickyNekroTopic starter

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Re: 7805 and 7V2 NiMh
« Reply #4 on: February 11, 2008, 03:19:41 PM »
Yep I know...
I was just confused... cause the NiMh voltage will drop as they being used to about 5V8 or lower...
Since I measure the voltage is ok but I though the regulator would just stop working after a point... I guess that was wrong after all...
So nice!!! Now I can start!!!

Thanks for the advice!!!


Cheers!!!
Lefteris
For whom the interrupts toll...


P.S. I've been inactive for almost a year... Don't give promises but I'll try to complete my tutorials. I'll let you know when..

Cheers!

 


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