I am making an autonomous car from an old RC car. For the steering I made my own H-bridge, consisting of 2 PNP and 2 NPN transistors. When I connect everything, the motor works fine. But it hasn't got enough power to turn the steering wheel (the steering motion works with gears). When I connect the motor directly to the 5V and GND of the arduino, the motor has enough power to turn the steering wheel. Does anyone know how to get more power out of my H-bridge? I tried decreasing the resistances on the bases of the transistors and I also tried using a 9V battery, but both didn't work out.

  • 1
    Can you show a schematic of your current setup? What power supply did you use before the 9V battery? Aug 31 '18 at 22:39

The 9 V battery is likely to be the problem, since it will not supply much power. Try lithium batteries, e.g. two Li-ion or Li-polymer cells in series, to make ~8.4 V.

Is there really a need to make your own H bridge? There are plenty of very cheap and compact modules available. The one I use for a lot of projects is TB6612FNG (15 V, 2 A maximum, 2 channels).

  • I ordered an L298N H-bridge but it still hasn't been deliverd. So I made my own. But why does a 9V battery supply less power than Liithium ion batteries? I just asked myself the question: How could the original RC car turn it steering wheels and why can't I do that with a 9V battery directly attached to the motor? Than the problem is probably the battery as you said. The original RC car used 6V. Should I buy Li-ion batteries then?
    – jan
    Sep 1 '18 at 11:37
  • The chemistry of alkaline batteries in general, not only the 9 V one you are using, does not lead to high current draw. You will easily find more information via Google/wikipedia.
    – MichaelT
    Sep 2 '18 at 14:15

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