L298 motor driver wired in parallel

Other Hardware Motors, Mechanics, Power and CNC
1

Hello good people of the Arduino forum.. I finally got around to registering after reading a fair few posts around here over the past couple of years.
Unfortunately, the main reason for registering is that I have come across a problem that I cant seem to get past.

I am trying to drive a motor with stall current of 2.5A bi-directionally with an Arduino Nano. I wanted to use the L298 (I tried two L293NE chips piggybacked but they were over heating), and wired the inputs and outputs in parallel to get it up to a max current capacity of 4A

I have wired the L298 exactly like this:

When I connect both of the Enable (EN) wires, one of the 'In' pairs (eg 'In 1' and 'In 4' together) and the logic supply to a regulated +5v supply, and the motor voltage supply to +9V, the motor runs just fine, and that works in both directions.

My problem arises when I try to connect the two EN wires and an 'In' pair to digital outs on my Arduino. I want both EN wires to be controlled by one Arduino pin for PWM, and each 'In' pair to be controlled by one pin each (simply set them to high or low). I believe the Arduino can't supply enough current to a single pin to drive 2 EN wires, or an 'In' pair.

For the moment, I am just trying to get the EN wires working (one step at a time!), so I've wired 'In 1 & 4' to the regulated +5V to make sure that is getting what it needs and left 'In 2&3' disconnected. I tried using a 2N3904 transistor with the Base on Pin 9 on my Arduino (Set to High in the extremely simply code), regulated +5V on the Collector and the EN wires connected to the Emitter, followed by a 10k resistor, then going to GND. The motor just runs constantly regardless of whether the Arduino is even connected or not and it seems to be ignoring the transistor which should be stopping the flow between the +5v and GND

Can anyone help please? I seem to have exhausted Google's capabilities searching for an answer. I did find this:
http://www.ikalogic.com/4a-h-bridge-motor-driver-using-the-l298-ic-schematic/
which is where I got the idea for the transistor, but I really want my EN wires and 'In' pairs kept separate from eachother.

2

The L298 inputs take less than 1mA each, so an Arduino can easily drive a pair of them. Your 2N2904 buffer won't work, because the L298N inputs source current, which your driver needs to sink. Connect the L298N inputs directly to the Arduino instead.

3

Thanks very much for the quick reply.. I did try that at first but couldn't get it to work. I may have done something silly, so I'll try again this evening.

I took some readings with my multimeter when it was connected and I was worried about them - When I read the voltage between Pin 9 on the Arduino (while connected to the EN wires) and GND, it was getting 5V which I expected. But when I took the reading between the breadboard connector I made to connect the two EN wires to pin 9 and GND, it read around 8V, and I figured that was why it wasn't working - the max input Voltage is 7V

Any clue why I'd be getting this reading?

4

Did you remember to connect Arduino ground to L298N ground?

5

It was bugging me so I sneaked out of work early to go and check everything over. Turns out it was just a bit of shoddy soldering that I somehow missed when checking and rechecking that all the contacts were separated - one of the enable pins had shorted with the motor voltage and it was sending over 8V down the enable wire!
It appears to be working now. With another Arduino - my nano is being difficult and doesnt want to take any programming now :-/
Thanks so much for taking the time to look at my problem

6

Glad you got it working! Have fun.