I have the following situation: H-bridge with a 12V - DC motor.
I used 2 9V - batteries and made a voltage divider to have 12 Vout for the motor.
But this doesn’t work. I measured Vout and it was 12 V.
When I didn’t use the voltage divider, and attached 18 V to the motor, it worked.
Can somebody explain this?
I have another analog motor that I will attach to the right side of the H-bridge, but then my question is
the amount of current I need to provide to the motor voltage input pin (there is only one of these pins on
the newbie, yet full in progress in my own project, but with more downs that ups, but will get there…
fig 1 = motor I used
fig 2 = scheme with voltage divider
fig 3 = scheme without voltage divider (this works)
Off hand, I would say that motor requires more current than those batteries can supply.
You cannot use a voltage divider to provide a power demand.
Current delivery of voltage dividers should always be considered as 0 ( to permit the R1/R2 ratio provide the calculated voltage)
Since power is the product of voltage x current then power = 0
You need batteries capable of a decent current output - small 9V batteries are
hopeless for powering motors. Consider LiPo or SLA or NiMH rechargables -
motors require amps, not milliamps.
You also need to do some calculation for capacity - how much current is your
application using on average? How long do you want it to run for between
charges or battery-changes?
Brushed DC motors like that one have a minimum current needed to overcome
friction, and are only efficient at the higher end of their power range as a result,
which means choosing the right size of motor is important for maximising