Any guidance on controlling an L298 with one set of input going to both motor controllers and coupling the outputs in parallel or series to allow doubling of the voltage or the current capability to a single DC motor?
Cheers Alan
In series for double voltage seems impossible to me.
You can use them parallel, with a single Rs (sense resistor).
According to the datasheet: For higher currents, outputs can be paralleled. Take care to parallel channel 1 with channel 4
and channel 2 with channel 3.
Peter_n:
In series for double voltage seems impossible to me.
You can use them parallel, with a single Rs (sense resistor).
According to the datasheet: For higher currents, outputs can be paralleled. Take care to parallel channel 1 with channel 4
and channel 2 with channel 3.
Please help a simple mech eng... why is it impossible to put into series? Can they not be treated like two batteries...
When they would be used in series, one of them is connected to ground, and the 'ground' for the other one to something in between. So also the control signals should be related to that 'ground' in between. That is impossible, since any change to those signals will delay them, and that would cause one driver to act faster than the other.
There is another practial problem: when used parallel, one can take a little more current than the other one. That is not a problem. Also a little difference in delay is also no problem, since they can handle some peak currents.
When used in series, any change will have great influence, and they can not handle a peak voltage, so they will blow.
You can't put them in series, it makes no sense. The motor terminal voltage change
is experienced by anything connected to it, so if the motor terminal goes from 0V to
80V, so does the chip driving it, which if it is rated at 40V is going to be an issue.
You could have floating supplies for each H-bridge chip and opto-isolated inputs
if you really wanted to do it, but there are still issues with guaranteeing fair
voltage sharing when the switches are off/open, otherwise you just exceed the
breakdown voltage due to the spread in leakage currents between different devices.
1200V IGBTs are available these days so anything upto about 900V is relatively
inexpensive and straightforward to do as a single bridge (certainly less problematical
than having two matched floating supplies).