Qik2s9v1 Issue

I have a an issue with one of my Qik2s9v1. I have 5v going to power the controller from one source and 9.5v powering the motor side of the controller from another source. When I send commands to each motor seperately they work fine. When I send comands to both motors at the same time, the 9.5v power conections drops to less than a volt and ofcourse it does nothing. I have to unplug the 9.5 battery source and plug it back in to get it to go back to the 9.5v output.

This same setup works fine with another Qik2s9v1. The Demo mode does not seem to work all that well either, it is really slow to start. These are both brand new controllers. I ordered one to replace it as I really need to get this going. Looks like I will have to rebuild my entire curcuit as I am not good at desoldering. :frowning:

Any Ideas?


Your description of the problem makes it sound like you have a short between the motor driver outputs of your misbehaving qik. Can you use a multimeter to check for shorts? Is it possible that the qik is sitting on a conductive surface that is shorting the leads together or that you have an unintentional solder bridge between the driver outputs? It would be helpful if you could post a picture of your setup.

- Ben

I did not have physical short with my setup. Setting the max speed on M1 to 127 caused my system to short out. When I dropped the max speed to 90, it worked fine.

Thank you.

Those test results are indicative of a power supply issue, not a short; it seems like your power supply simply cannot deliver the power your motor is trying to draw when you set the speed above 90 or when you use two motors. What kind of battery are you using and what are the specs of the motors you are using (e.g. stall current).

- Ben

Ben, I have a crazy setup with 3 Pololu gear motors on each side of the MotorController connected in a series for a total of 6 motors. Before you get started with your response, I fully understand this not be the best method, but I am trying to keep my project under a certain weight. The built in demo worked great because it does not use both sides of the MotorController at the same time. For power I have 9.5v that include (2) 3.7 lipo batteries in a series connected to a Pololu 2.4v-9.5v booster.

My mistake was not trying something more simple at first as this was the first time I was working on the software side of my project and outside of the built in demo mode as well. My project is doing what I want it to do perfectly, but I will not give it more speed than 90 as mentioned in my previous comments.

Take it easy on me,

That sounds like quite the project! We carry a lot of gear motors; can you provide the product number or link to the specific ones you’re using?

Do you have a good reason for not just using the batteries to directly power everything? The boost regulator is going to be the bottleneck for the current you can deliver: while the qik can deliver a continuous 1 A (3 A peak) on each channel, the boost regulator won’t be able to deliver much more than one amp total in your system, so it’s going to be holding you back. When you try to draw more current than the regulator can handle, the over-current shutoff will kick in, which is likely why you start measuring an output of under a volt when you try using both motor driver outputs or running one side at speeds over 90. If you remove the regulator and connect the batteries directly to the qik, do things start working better?

Another reason demo mode works well is because it accelerates the motors gradually, which draws less current than commanding a motor at rest to move at full speed. Demo mode does briefly drive the motors at full speed, so it is possible for your system to get speeds above 90 if you actively limit acceleration (and keep the load on the motors down).

One other thing to consider is the way you’re connecting your motors. When you connect motors in series, if one motor experiences a heavy load or is completely stalled, it starts to draw all the power and the other motors get weaker. If you connect your three motors in parallel, this does not happen, although you then need to be able to provide three times the current.

- Ben

Hi Ben,

The motors I am using are part #198, 6 V: 320 RPM and 80 mA free-run, 25 oz-in (1.8 kg-cm) and 1.6 A stall. Correct me if I am wrong, but the reason I went with a booster is to get to 9.5v with the (2)3.7v =7.4v battery source and to maintain the 9.5v even if my batteries got a little low. This seems to me to be a similar concept on the 3pi robot.

Thank you,

We don’t have a product #198. Product #1101 (100:1 micro metal gearmotor HP) matches the specs you describe. Is this the motor you’re using?

Running the motors at a constant voltage is nice for certain applications, but it’s more of a luxury than a requirement for typical robotics applications. Most hobby robots I’ve seen have motors powered directly from batteries. One reason the 3pi uses regulated voltage for the motors is because the battery voltage transitions from above 5 V when fully charged to below 5 V when drained, so boosting provides a voltage that can then be regulated down to a constant 5 V for the logic. Note, however, that the 3pi uses the non-HP versions of our micro metal gearmotors, which have a stall current of only 360 mA at 6 V. The HP versions draw more than four times the non-HP current at stall.

In general, I think you probably need to rethink your design some. Using your motors in series means that each motor only gets 1/3 of your total motor voltage across it when all conditions are equal (which is only around 3 V), and as the load increases on one motor, the other motors in series with it will get slower and weaker. If you really need three motors per channel, I think parallel connections are the way to go, but you’ll need a substantially beefier motor driver, such as the qik 2s12v10 or our Simple Motor Controller 18v7, and the boost regulator will not be sufficient. Since a parallel connection means each motor will see the full motor voltage, you could use a step-down regulator instead, such as our 7 A D15V70F5S3, to give the motors a fixed 5 V (still more than the 3 V they’re each seeing now). You could also try replacing your motors with non-HP versions.

If you want to make things work with your current motor controller and motors, there are a few things you can try:

  1. As I suggested before, try things without the boost regulator. It might work well enough for your needs.
  2. Implement acceleration limiting in software to decrease the current draw of your motors when they are speeding up or changing direction.
  3. Run the motors only at low speeds and avoid situations that will put a lot of load on the motors.
  4. Consider removing one of your battery packs and boosting to a lower voltage, which will cause the motors to draw less current. For example, boost a single 3.7 V battery pack to 5 V or 6 V. Of course then each of your three motors will have even less voltage across it, which might not work so well.

What it ultimately comes down to is that the parts you’re working with right now are not well matched. You have an underpowered motor controller and regulator for your motors (at least the way you want to use them), so it’s going to be tricky to make them all play nicely together.

- Ben