50$ robot - problem with programmer

[bens]

I still can't give you any information without knowing what kind of current they draw (specifically free-run current and stall current, which is the current the motor draws when the motor shaft is held fixed and not permitted to rotate).

- Ben

[karlis]

i`m sorry Ben but i didnt realy catch what you are thinking about ;(

motor normaly runs with 3v just plug and go its runing, if i could understand what more you need to know, maybe i could understand H-bridges bether

[bens]

When you put 3 V across your motor terminals, how much current do they draw?  Some 3 V motors might only pull 200 mA at stall while others pull 2 A at stall.  Different H-bridges will be capable of supplying different amounts of current, so you need to know what current your motors will draw before you can pick an appropriate H-bridge.  Does this make sense?

- Ben

[karlis]

Yes a litle, and i`m sad to say but i dont know how much amps can they draw, on stearing motor there are ceramic capacitator (104) but on drive motor (rear) there are two ceram. capac. (104)

just did a litle test, while my robot does not move, i use temporaly power supply (old cellphone charger) output ~7v

i connected the wires and found out that for stearing its ok, stong and fast pull, but for driving it was kinda lazy, maybe cuz of low apms

on charger are these nummbers
230v/~/50Hz/20mA/4.6VA
??/??/??/300mA/1.5VA
(under ?? nummbers are worn out - not visible)

[bens]

Basically you'll need a multimeter if you want to measure the current.  If you don't have a multimeter you should get one; it will serve you well if you plan on working with electronics and embedded systems.

- Ben

[karlis]

if multimeter mesures volts apms resistance etc then i have 1

shen i attach wires to motor, i should put connect multimeter to mesure amps right?

[bens]

Yes.

[karlis]

well then if i mesured corectly, and i think i did then nummbers are:
drive motor fwd 5.6Amps
                 bwd 6.6Amps

stearing motor had ~3Amps, i thing if i would keep power longer than 5-10secs, amps would climb up to 5 or 6, i didnt wanted to burn it so i swiched them off prety fast, and 3amps is what i saw

strangely that without multimeter it ran slower than with, how comes that ?

[karlis]

so what H-bridge i should get ?

ps sorry for double-post

[bens]

I need to know the stall current.  What this means is that you need to run the motors and see what the current is for each when you don't let it spin (hold it stalled).  It sounds to me like you were measuring free-running current.  Is this right?  And if your free running current is 5 A, you must have some pretty beefy motors...

Also, what voltage were you running these motors at during this test?

- Ben

[karlis]

i sayd befor, ~7v power from old cellphone charger, i added 1 end of charger to motor, other lear from motor to multimeter, and 2nd multimeter wire with chargers last one, then i turned power on and saw 5A, didnt hold it nothing, just let it spin...

i should hold motor, so i cannot spin, and then mesure amps ?

[bens]

i should hold motor, so i cannot spin, and then mesure amps ?

Yes.  You should also make sure your cell phone charger can deliver enough current...

- Ben

[karlis]

i have mesured them and i`m a bit confused, because on 2 diffrent multimeter setting got 2 diffrent reading

1. multimeter setting 10apms max
stall current 0.3 - 0.7 amps
2. multimetter setting 200m amps
stall current 5-7amps

i dont think that 2nd mesure is correct, because of the size of motor, i have compresor who uses 16amp fuse and its aint gona working on 7volts (4.5kw motor)

could ~0.5amps be true ?

[karlis]

I`m waiting for ansver dudes

[Admin]

could ~0.5amps be true ?

yeap that sounds about right

[karlis]

so what h-bridge should i search for ?

[Admin]

Any motor driver that can handle more current and voltage than you plan to use for your motor.

Basically, you will have to stare at datasheets for awhile

The Axon can control any motor driver.

[Webbot]

My Controller Tutorial may help http://www.societyofrobots.com/member_tutorials/node/159