February 9, 2019

Big Dyno Up And Running

A long overdue progress update on the big dyno.

The torque sensor got new electronics Bayley designed, which have a built in power supply, A/D, and micro, to convert the signal to digital as quickly as possible.  I made a nice box to house all the electronics:

The torque sensor mounted, with the absorber on the right and the motor under test on the left:

To power and control the test motor, there's a bank of terminals for DC input and motor phase output, if you want to drive the test motor with the Prius inverter built into the dyno.  And quick disconnect fittings for water cooling the test motor:

Speaking of inverters, here's a look under the sheet metal covers:  Underneath are two Prius "bricks" mounted to a big waterblock.  Although the Prius power modules have two 3-phase inverters each, we had to use two of them so we could separate out the DC link current measurement for the inverter powering the test motor.

The dyno has an internal Mac Mini with linux on it, runing a fork of my dyno software.  Thanks to the cross-platform-ness of Python and Qt, all I had to do was install all the libraries and change the "COM" serial ports to "/dev/ttyUSB" and it just worked.  Yes, that's the "Hybrid Synergy Drive" plaque from the Prius power module covering up the Apple logo:

To go with the computer, it has a built-in monitor which can be raised and lowered for storage:

The absorber and all the sensors work, and we've helped the FSAE team do a little bit of testing on their new motors.  Next up is populating the second half of the control electronics so the dyno can control the test motor.  Then we'll be able to do a full optimization of the Sonata HSG and get even more power out of the big kart.


  1. Very nice. Are you using the gigatroller in this design or is everything prius inverter? Any details on the motor controller side would be great!

    1. Prius inverter. The motor control side is a newer revision of the go kart electronics. I expect Bayley will to a writeup at some point.

  2. Oh, cool. I figured that might be the case. How small a motor do you think the prius inverter could go down to? Is there enough resolution to drive small motors, like one of the large skateboard motors you were using for your previous absorber?

    1. The Prius inverter only switches at 5 kHz in the car. We've pushed it to 10, but it's not super happy about it - internal delay and minimum/maximum duty cycles really hurt you at 10 kHz. The other downside with using it with small motors is that it's IGBT-based, so it's going to be inefficient on low voltages due to the couple-volt drop of the IGBTs

      The big dyno will eventually have a DC-DC converter like the small one does, so you'll be able to hook up whatever motor controller you want for the test motor. But for smaller things I still have the little dyno.