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If I was to connect two motors in parallel instead of just the one motor it currently has on each H-Bridge,, would the transistors on the motor controller blow?

I have this motor controller - here is a schematic & table as well: schematic

arrowThe lowest pin on the connector is pin 7 -------- The lowest on this connector is pin 1 arrow

table

I am controlling this using my Raspberry Pi, connected to the first 4 pins and last pin of the 7 pin socket - this is not relevant as such, but this outputs 3V3, and controls the H-Bridge.

An individual motor draws less than 0.1A at 6VDC, but on startup and stop can draw up 0.48A These measurements are from a multimeter, which will only take an average anyway.

Each motor has one of these already attached as well:

Here are the transistors:

Q7 - Q10 are 2SC3279 - NPN, can take 2Amps DC, 5Amps 1/100th of a second

Q11 - Q14 are 2SA1300 - PNP, can -2A DC, -5A also for 1/100th of a second

For more info on the controller see here

Here are some data sheets of the relevant transistors: 2SC3270 2SA1300

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  • \$\begingroup\$ I expect that there is an error in the Maximum Ratings table - a transistor having 2 mA max collector current wouldn't be very useful. The Electrical Characteristics table gives Hfe for 4 Amp, and Vce-sat at 2 amps which seem more reasonable for this application, and is a reasonable match for the NPN rating. \$\endgroup\$ Dec 7, 2013 at 19:24
  • \$\begingroup\$ If found this datasheet which seems 10 years updated compared to the original one I referenced to (this one). I shall update my question, @Peter \$\endgroup\$
    – Wilf
    Dec 7, 2013 at 19:58
  • \$\begingroup\$ I don't get it: The motor controller you have described already supports two motors, and has separate connections for each. So why would you need to parallel the motors? Other than that, yes, you certainly can wire up two motors in parallel, or even more, so long as the total starting current is within the capabilities of the drive transistors and the supply. \$\endgroup\$ Dec 7, 2013 at 20:53
  • \$\begingroup\$ No, instead of the two motors it currently powers, I want to run four - two controlled by one H-Bridge, two by the other H-bridge. The thing is, the peak current I get on my multi-meter from one motor starting is 0.48A (which is an average, so presumably at least a third smaller than the actual peak), so putting two in parrallel may double it, so starting the motors may blow the H-Bridge... @AnindoGhosh \$\endgroup\$
    – Wilf
    Dec 7, 2013 at 20:57
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    \$\begingroup\$ Thanks @AnindoGhosh , I just found the stall current is too big... \$\endgroup\$
    – Wilf
    Dec 13, 2013 at 16:45

1 Answer 1

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No, it won't take any more motors sad.

Just ran a few tests for two motors connected in parallel to the same power supply as would be used by the controller. - here are the results:

  • Measured start current: 0.88A at circa 4.9V
  • Measured running current: Anything between 0.2A and 0.6A, also circa 4.9V
  • Measured STALL current: Generally above 1.8A, voltage can drop to around 3V for one or both motors stalling, which also results in a current of around 2.2A, which is too big for the motor controller to handle...

Just have to find another one, I guess...

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