I want to power two motors. A 24v motor with a simple on/off switch, and then a 12v motor with speed control. The circuit will be powered by two 12v 10AH SLA batteries. And using a BTS7960 motor driver.
I am wondering if it is ok to wire the circuit as per the image below?
Things to note :
The 24v (to power 24 motor) is made up from the two batteries in series
The 12v (to power 12v motor and Arduino) is made up from only using one of the batteries
The BTS7960 motor driver itself is powered from the 5v output of the Arduino
The reason I ask is because when I built this circuit, I am seeing sparking (on the battery terminals) when I hook up the batteries, and in more than one case, the Arduino has been damaged and stopped functioning (no lights, no sign of life).
I have also tried the same circuit but with the Arduino instead being powered from a separate 9v battery, and also got the same results. In that it was fine until I hooked up the SLA batteries, which caused a spark at the battery terminals and the Arduino stopped working (no lights, no sign of life).
Hi, I completely agree on getting the 12v system up working first, I was just wanting to check that my plan is actually workable and there isn't something wrong in the design that would explain the sparking?
What are the power ratings of your motors?
The 12v motor is a windscreen wiper motor, draws about 2 - 3A continuous, but a lot higher on startup, of which I'm not sure as I can't measure it.
The 24v motor is a scooter motor. It's 250w
Which 12V battery did you connect the DC jack of the Arduino too?
I hope the battery connected to the BTS7960.
Hmm, I diodn't know it would make a difference and was connecting it to either one. Can you explain why it would make a difference?
Hi,
The battery on the driver is gnd referenced to same gnd as the Arduino.
The second battery is not, it has a potential that is 12V above the first battery, so effectively you were putting 24V on the DC jack, positive and 12V on the DC Jack negative.
SLA batteries are capable of more than 100A instantaneously if presented with a short.
You effectively shorted the first battery positive to its gnd, through the Arduino and let the smoke out.
You said you’re using the BTS7960 which is a seven pin device and then post a drawing that has twelve connection points shown with ten of those connected. How did the mosfet grow five extra pins? Based on the lack of accurate information, I’m not sure what you’ve done. Sure, it’s likely you blew up your Arduino but I cannot tell you how you did it, other than overvoltage, which always lets the smoke out.
Your original concept can work but the actual wiring is very important as it will requires star wiring (parallel) practices, not point to point (series) wiring - along with the proper wire sizes in the high current paths.
TomGeorge:
Hi,
The battery on the driver is gnd referenced to same gnd as the Arduino.
The second battery is not, it has a potential that is 12V above the first battery, so effectively you were putting 24V on the DC jack, positive and 12V on the DC Jack negative.
SLA batteries are capable of more than 100A instantaneously if presented with a short.
You effectively shorted the first battery positive to its gnd, through the Arduino and let the smoke out.
(Yes - I am using the IBT_2)
Ahhhh! I didn't realise the two GND inputs on the motor driver were connected! .. I assumed it was like a relay, where the output is not connected to the input.
So really, I don't even need to connect the GND of the DC Jack, as it's already connected. I just need to wire the DC positive like this :
According to the IBT-2 schematic, GND and B- are tied together on the pc board. The OP’s schematic with the added green line to 12V for the Arduino supply should work, once the damaged parts are replaced.
I’d expect the 74AHC244 buffer on the motor driver to be blown since its VCC source is from the Uno’s regulator. The mosfets are likely fried too since their logic side probably was hit with 12vdc so it’s time for both a new Uno and driver board.
