I am using the following circuit, with a LiPo 3S 11.1V (which charged, outputs 12.5V), with a split from the bat, one side to a regulator, that converts to 5V towards the Arduino and rest of chip legs, that need 5V and the other split side, stays 12.5V, for the motor that is switched on/off, by the chip via the Arduino, here is the schematics (in case you can’t see the link, a picture is attached) :
Why when bat is fully charged (12.5V), still, the motor gets only about 10.5V? Is it the grade of the pot i am using? should i use a higher quality pot? What would happen, if i used instead of that 10k pot a 5k pot? How can i get the full 12.5V?
If i want to have this circuit without a pot, just switch the max 12.5V on/off, without changing the voltage, what should i change in the circuit?
If you are using a pot (varible resistor) in series with the battery and motor than yes, there is a Voltage drop in the pot that follows Ohm’s Law.
The modern method to control motor speed is switching a power MOSFET with a PWM signal from the Arduino.
Do some web searches to find lots of info on doing this with an Arduino.
Edit:
The diagram showed up after I posted.
It looks like you are using the Pot to create a variable Voltage into the Arduino’s ADC.
I guess your code then changes the PWM duty cycle to the L298 H-Bridge. If the PWM is less than 100% then you will measure a lower than maximum Voltage with a DVM.
You need to use an O’scope to see the PWM duty cycle.
There are also some losses in the L298’s drivers so that could also explain the lower Voltage at the motor.
I just found out that there exist the technical terms: “typical high level output voltage and the typical low level”, which are the explanation for the voltage i get, since the chip is designed so, that it will deliver about 2V less. Is that correct?
If it is, the same person, also said that i should use a mosfet, instead of a chip.
I have a very important weight issue with my application.
Could i just as easily find a mosfet that will do the job, that weight is less than 0.5 grams, just as that chip is?
Will it be just as easy to find a mosfet switch circuit schematic on the web, that works with an Arduino?
Will this circuit do the exact same thing, as the circuit with the chip and pot, just without the pot function (which i don’t need anyway), and give me switching for max voltage? If so it is good for me, but a few more questions:
Will it work also with 12.5V battery and motor or just with up to 9V bat and motor? The mosfet type is: irf540n, mofet weight: 3 grams.
Can i find a mosfet that will do the same thing, but weight less? Do you know that mosfet model number? If there exists such a mosfet, should the circuitry be just the same, just replace the mosfet model?
A couple of questions first. The '293 driver IC is often used as a ‘H bridge’ driver, meaning that w/the proper commands you can spin a DC motor in both directions. You didn’t have yours wired that way … can we assume you want the motor to turn in 1 direction only ?
If true then using a FET w/the proper ratings will work. It’s effectively a switch to ground, completing the circuit. Do you know the current draw of your motor ? W/o knowing the current draw of your motor I can’t say for sure but I’m willing to bet that the irf540n will work with any hobby motor you’d have. Perhaps a lessor FET would suffice.
You are missing a resistor or 2 on your diagram above, see this thread.
I am intending to use a LiPo 1A 25C 3S 11.1 volts (charged 12.5 volts).
The Arduino is for switching the motor on and off from a bluetooth.
The continuous current of the motor is around 3 Amps and the stall current is somewhere between 40-60 Amps, but i don’t believe it will get any close to that, since it will run a liquid pump and either pump the liquid or be shut off.
But, maybe i don’t understand well enough the term ‘stall’.
With the weights of all the other items, I find it hard to believe the 3g FET should be your prime concern. Besides the weight of a TO-220 package is just under 2g.