NIMH batteries and amperage output
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HI all. I have a small rover that runs on 4, AA batteries. I had been using
700mah Nicads, but they kept forcing the rover into reset mode after 5-10
minutes. I put a 4700 mah cap across the battery leads. I put .01 caps
across the stamp power input and the H bridge chip as well.
My robot has the basic stamp, driving an H bridge (SN754410), which then
drives 2 small motors. I am using a devantech srf04 for range finding. +5
from battery goes thru a
lm2940 regulator for the electronics, and I run the raw voltage to the H bridge.
I tied all grounds together also.
I went out and bought Energizer NIMH batteries rated at 1700 MAH. Now the
robot wont work at all. The robot goes thru initialization routine, into its
first command to ask for data from the srf04 and then shuts down and resets.
I went back to the 700mah batteries and the robot runs again, but only for a
short time. (just to prove I did not knock a wire loose)
I had thought these NIMH batteries were supposedly great for digital
cameras. Those cameras have a large amp draw to charge batteries, so why
wont they work in my robot?
What size cap would I need to provide surge power for when the 2 motors run?
I am limited for space, hence the AA batteries. And I dont have a heck of
alot of room for a huge Capacitor either. Sorry I dont know the true
amperage draw of the motors themselves, they were in a toy 6 wheeled rover
that I modified for the Stamp to run.
Any advice would be appreciated.
Very respectfully, your obedient servant.
Kerry
Admin@M...
WWW server hosting [url=Http://mntnweb.com]Http://mntnweb.com[/url]
Kerry Barlow
p.o. box 21
kirkwood ny
13795
607-775-1575
700mah Nicads, but they kept forcing the rover into reset mode after 5-10
minutes. I put a 4700 mah cap across the battery leads. I put .01 caps
across the stamp power input and the H bridge chip as well.
My robot has the basic stamp, driving an H bridge (SN754410), which then
drives 2 small motors. I am using a devantech srf04 for range finding. +5
from battery goes thru a
lm2940 regulator for the electronics, and I run the raw voltage to the H bridge.
I tied all grounds together also.
I went out and bought Energizer NIMH batteries rated at 1700 MAH. Now the
robot wont work at all. The robot goes thru initialization routine, into its
first command to ask for data from the srf04 and then shuts down and resets.
I went back to the 700mah batteries and the robot runs again, but only for a
short time. (just to prove I did not knock a wire loose)
I had thought these NIMH batteries were supposedly great for digital
cameras. Those cameras have a large amp draw to charge batteries, so why
wont they work in my robot?
What size cap would I need to provide surge power for when the 2 motors run?
I am limited for space, hence the AA batteries. And I dont have a heck of
alot of room for a huge Capacitor either. Sorry I dont know the true
amperage draw of the motors themselves, they were in a toy 6 wheeled rover
that I modified for the Stamp to run.
Any advice would be appreciated.
Very respectfully, your obedient servant.
Kerry
Admin@M...
WWW server hosting [url=Http://mntnweb.com]Http://mntnweb.com[/url]
Kerry Barlow
p.o. box 21
kirkwood ny
13795
607-775-1575
Comments
The motors going through main battery pack tends to generate too much RFI
and the brownout surges are almost impossible to tame. If you put in a big
enough capacitor to smooth out the brownouts, you then have problems where
the circuit still runs after you turn it off. The capacitor can also furnish
an almost infinite power surge on it's own, which can burn out transistors
on the PCB too.
You might try putting in a 5k pullup resistor on the reset line and a .01 or
.1ufd cap on the reset line to ground. The problems could be noise getting
in on the rest line restting the MCU or brownouts (actually instantaneous
spikes) taking it too low causing resets. If the motors aren't too strong
this may work.
Original Message
From: Kerry Barlow [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=nffgFjhdxiUwRM8AF7SchzvM8u4AZdgChV8FOLpUDRWYpb84KJDmYJmFzLi4vobKEpGCWgEO_vg]admin@m...[/url
Sent: Friday, August 09, 2002 1:42 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] NIMH batteries and amperage output
HI all. I have a small rover that runs on 4, AA batteries. I had been using
700mah Nicads, but they kept forcing the rover into reset mode after 5-10
minutes. I put a 4700 mah cap across the battery leads. I put .01 caps
across the stamp power input and the H bridge chip as well.
My robot has the basic stamp, driving an H bridge (SN754410), which then
drives 2 small motors. I am using a devantech srf04 for range finding. +5
from battery goes thru a
lm2940 regulator for the electronics, and I run the raw voltage to the H
bridge.
I tied all grounds together also.
I went out and bought Energizer NIMH batteries rated at 1700 MAH. Now the
robot wont work at all. The robot goes thru initialization routine, into its
first command to ask for data from the srf04 and then shuts down and resets.
I went back to the 700mah batteries and the robot runs again, but only for a
short time. (just to prove I did not knock a wire loose)
I had thought these NIMH batteries were supposedly great for digital
cameras. Those cameras have a large amp draw to charge batteries, so why
wont they work in my robot?
What size cap would I need to provide surge power for when the 2 motors run?
I am limited for space, hence the AA batteries. And I dont have a heck of
alot of room for a huge Capacitor either. Sorry I dont know the true
amperage draw of the motors themselves, they were in a toy 6 wheeled rover
that I modified for the Stamp to run.
Any advice would be appreciated.
Very respectfully, your obedient servant.
Kerry
Admin@M...
WWW server hosting [url=Http://mntnweb.com]Http://mntnweb.com[/url]
Kerry Barlow
p.o. box 21
kirkwood ny
13795
607-775-1575
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voltage drop under heavy loads. I've heard newer ones are better.
> I had thought these NIMH batteries were supposedly great for digital
> cameras. Those cameras have a large amp draw to charge batteries, so why
> wont they work in my robot?
> What size cap would I need to provide surge power for when the 2 motors
> run?
Remember the start up current of motors will be much higher than the running
current. Also if they stall current goes up.
> I am limited for space, hence the AA batteries. And I dont have a heck
> of alot of room for a huge Capacitor either. Sorry I dont know the true
> amperage draw of the motors themselves, they were in a toy 6 wheeled
> rover