Answered: Question about new Power Expander

I was really excited to get my Power Expander this week, but I can’t seem to get it to work. I have it connected to a new and freshly charged 7.2 volt battery that I also ordered and the status LED is green. However, no matter what I do with the transmitter (which I have tethered to the microcontroller) nothing happens. If I plug the motor directly into the motor port of the microntroller, it works fine. When I have the status port plugged into one of the Analog inputs on the microcontroller, the status LED is red.

I have tried both 7.2 volt batteries that I have and nothing seems to change. I followed the instructions on the Inventor’s Guide Insert and don’t know what else to do. Do I just have a bad Power Expander or am I doing something wrong?

Any help that you could give me would really be appreciated.

Can you send a picture of your setup to Also be sure you do not connect the Status Cable from the VEX Power Expander to a Digital Output on the VEX Microcontroller - it should be connected to a Analog Input.

I will try to send you a picture of my setup as soon as I can. I double checked just to make sure and the Status Cable from the Power Expander was plugged into an Analog Input on the microcontroller.

Using the Power Expander seemed pretty straight forward and I checked my connections several times to make sure that I hadn’t plugged something in wrong.

**Also, send your Hex file of the code you have in the Microcontroller along with the picture of your setup.

If we do not see anything from your setup picture, we will issue an RMA (Return Merchandise Authorization) Number for the return of the product.

Thanks for all of your help with this. I sent the pictures of my setup last night - did you recieve them?

I will send you a copy of the code that I have in my microcontroller. It is in EasyC V2. I recently downloaded the latest version with VEXnet support and loaded master code 8 into my microcontroller. The program was an old one that I had and I just made a few changes to it to read the Status from the Power Expander.

**After further evaluation, it was determined that the VEX Power Expander IN and STATUS Port had the PWM Cables installed backwards. This can not be done if you are using the VEX Keyed PWM Cables.

We will update the VEX Inventor’s Guide with the following:
Note: When using Non-Keyed PWM Cables on the VEX Power Expander, the Gnd/Blk wire should be closest to the key slot on the STATUS and IN Ports, and it should be the furthest from the key slot on the OUT ports.**

I’m really sorry for all of the trouble I never even thought about the cables being in backwards. I never really paid any attention to the female end of the keyed PWM cable that I have. I usually use the non-keyed cables and the male end always plugs into the ports on the microcontroller with the white wire on the side with the key. I just followed the same rule when I plugged the female ends into the Power Expander.

Thanks for adding the note to the VEX Inventor’s Guide. Hopefully, it will prevent someone else from having the same trouble with their Power Expander.

Thanks again for all of the help, I really appreciate it.