Archive for April, 2012
a quick start:
questions for consideration:
snake or eel( float or sink)
propeller for forward propagation?
behavioral test – think better about mechanics of aquatic locomotion
Here are some images of the progress:
my email to the p comp list:
It turns out something weird is happening with my batteries – I can run the lipo batteries I have with two DC motors, giving me a current draw of 1800 mAmps (around there anyway when I tested with the multimeter)m, at around 8 V .
When I try to power solely one servo, the voltage drops immediately to below 2 V. The batteries seem to be fully charged , as indicated by the charger I’m using and when I try to give them voltage from a power supply of 8.4 volts at 0.25 mAmps limit, the power supply shuts to 0 (I think this happens with LI ion batteries, a chip prevents over charging if using a regulated power supply…?)
Anyway, what can possibly be preventing me from running one servo with a current rating of 0.3 Amps peak , but I can run DC motors , with 1800 mAmp peak? ?
I can’t figure out what might be wrong – if the battery was damaged, I thought I’d not be able to use it for the DC motors, but since it works fine that way… what can be the problem?
OK another Totally Weird thing is happening:
when I try to test the amperage on one servo by plugging the multimeter in series between the battery +7.4 V and the servo + power , the servo DOES seem to move a bit (slower than when I use just a 6V non rechargeable battery).
When I but without the multimeter in series I get no motion (immediate voltage drop to 1.5 V from 7.4)
Also, the multimeter is reading 0 amps even when in series with the battery and Vin on the servo
SO I realized I can’t stack it… UGH. I dont understand why I can’t combine two LI ion batteries to make 7.4 V from 3.2 V. WHy?
And now I am using vivitar batteries from cameras, but my voltage regulator, which brings the voltage down to 5.8 V gets super hot. this scares me.
Also, the small servos get super hot. Especially the Emax MD (i’m also using Emax A ).
SO I think I’ll buy some larger servos now, from servocity , as well as perhaps a 6 V NImh battery. Ugh.
get bigger servos
get new battery
put more screws on black servos
put on loctite
test o rings
put dielectric / marine grease
seal with epoxy the rest of the large servos
get more vacuum tubing
figure out battery pack, arduino power, face, etc
logging voltage here: http://www.levinegabriella.com/bellflower/bellflower_dataLog.txt
arduino code here:
php and more to come…