I will be running a motor using L293 and 3s lipo battery. The lipo has a maximum voltage of 12.6V and I'd like to use up to 9V only.
Zener diode is the easiest choice but I couldn't but the right one for my project.
I'd appreciate any suggestions for any circuit, chip, or even the term I can google for this! Thanks in advance.
Buck converter.
Following AWOL's lead, here is a link to a down-converter on eBay:
AWOL's solution will more efficient than other solutions, so your battery will last longer on each charge.
Just a little more information about why a zener would not be an appropriate solution.
We will for this description assume the zener is an ideal zener in that it will always conduct at 9V
If you put a 9V zener across a 12 volt battery. The zener will act like a very low resistance for any voltage above 9V.
So imagine you have a 12.7 lipo batteries. What kind of load would you put on the batteries to immediately drag them down to 9V? Essentially that is what the zener would do.
If you added a resistor in series with the zener to reduce the current. This resistor would also limit the current to your load.
I hope this helped and not cause more confusion. I tried to put a lot of info in a small post.
BTW I'm curious why you wish to use only 9V from your battery?
John
If we only knew the current draw of that motor...
The L293 is an old/lossy chip, and will typically 'loose' about 2.6volt at 600mA motor current in H-bridge mode.
A 3-cell Lipo seem the perfect match for a 9volt motor and that chip.
Leo..
AWOL:
Buck converter.
I'd like to use any voltage below 9V, not just a fixed voltage, which I believe the buck converter will give. Unless a buck converter will output the same input below the voltage it is set, then this should be OK. I will test this, I have available buck converter modules.
Wawa:
If we only knew the current draw of that motor...The L293 is an old/lossy chip, and will typically 'loose' about 2.6volt at 600mA motor current in H-bridge mode.
A 3-cell Lipo seem the perfect match for a 9volt motor and that chip.
Leo..
The total current draw of the two motors is 800mA at stable spin. I thought about that also and should be fine most of the time, but, when paranoia kicks in, I'd like to make sure the DC motor does not exceed the 9V it is rated for. And also this question will help me in my other designs, so I'd like to really know an airtight solution.
JohnRob:
Just a little more information about why a zener would not be an appropriate solution.We will for this description assume the zener is an ideal zener in that it will always conduct at 9V
If you put a 9V zener across a 12 volt battery. The zener will act like a very low resistance for any voltage above 9V.
So imagine you have a 12.7 lipo batteries. What kind of load would you put on the batteries to immediately drag them down to 9V? Essentially that is what the zener would do.
If you added a resistor in series with the zener to reduce the current. This resistor would also limit the current to your load.
I hope this helped and not cause more confusion. I tried to put a lot of info in a small post.
BTW I'm curious why you wish to use only 9V from your battery?
John
Yes John, that is also my very concern. I think it will just blow the zener off if I use it! It is an RC tank toy that is why it is imperative to be on battery.
I'd like to make sure the DC motor does not exceed the 9V it is rated for
DC motor voltage ratings are a suggested maximum, not absolute. At higher voltages the motor will simply spin faster and wear out a bit more quickly.
If you use PWM and a motor controller for speed control, there is no need to worry, especially with that old, inefficient motor driver. See post #4
glenntamayo:
I will be running a motor using L293 and 3s lipo battery. The lipo has a maximum voltage of 12.6V and I'd like to use up to 9V only.
With power electronics the normal approach is to use PWM, never to reduce voltage in an analog way,
since PWM is efficient and doesn't need lots of heat dissipating (or here reduce battery life).
Using PWM and restricting the maximum duty cycle to 80% or so requires no extra circuitry and performs
better anyway...