How do you add heat sinks to the Pololu Dual VNH5019 Motor Driver Shield for Arduino?
- What heat sinks do you use?
- How are they attached?
- on top or under the board or both?
- if under the board, how do you prevent shorts?
Steve
Hello.
Why do you want to add heat sinks?
I want to add heat sinks because the user manual states that the actual current rating will depend on how well you can keep the chip cool. The device can only deliver 30 A for a few milliseconds. The manual states that the performance can be improved by adding heat sinks. One one the motors I will be driving with this device has a 30 A stall current. I would like to detect that the motor has stalled and take action in the software before the built in protection kicks in.
Excerpt from manual:
Real-world power dissipation consideration
Each motor driver IC has a maximum continuous current rating of 30 A. However, the chips by themselves will overheat at lower currents (see the table above for typical values). The actual current you can deliver will depend on how well you can keep the motor drivers cool. The shield’s printed circuit board is designed to draw heat out of the motor driver chips, but performance can be improved by adding heat sinks. In our tests, we were able to deliver short durations (on the order of milliseconds) of 30 A and several seconds of 20 A without overheating. At 6 A, the chip gets just barely noticeably warm to the touch. For high-current installations, the motor and power supply wires should also be soldered directly instead of going through the supplied terminal blocks, which are rated for up to 16 A.
Many motor controllers or speed controllers can have peak current ratings that are substantially higher than the continuous current rating; this is not the case with these motor drivers, which have a 30 A continuous rating and over-current protection that can kick in as low as 30 A (50 A typical). Therefore, the stall current of your motor should not be more than 30 A. (Even if you expect to run at a much lower average current, the motor can still draw short bursts of high currents, such as when it is starting, if special steps are not taken.)
Hello.
A motor with a 30A stall current should usually use well below that, so these drivers should be fine without extra heat sinks. You can use the current sense to monitor the motor situation, and if the stall is really abrupt, you would just need to turn off power, which is what happens in the overcurrent situations, anyway.
If you try it and are just barely exceeding the normal thermal issues, you might be able to help your situation with some heat sinks. There are all kinds of them, and it’s pretty much up to you: the bigger the heat sink and the more airflow you use, the more cooling you will get. You can uses double-sided tapes, thermal epoxies, or mechanical arrangements (e.g. screw the boards and heat sinks to various things such that the heat sink is pushed down on the motor drivers), and there are all kinds of thermally conductive, electrically insulating products for use with heat sinks if you’re concerned about shorting stuff out. Typically, though, you’d have the Arduino or other board under the shield, so there practically isn’t much space for putting heat sinks on the bottom side of the board.
- Jan