Rotary Encoder – built into motor for Electric Car

My electric Dodge neon uses an AC motor and an industrial motor controller.  I upgraded from m 1984 motor controller to one less than 25 years old (actually less than 5.)

The new controller does much more than the old one and has the ability to do some fancy tricks.  At the moment I am running it in “sense vector” mode.  The controller senses the position of the armature by monitoring the current in the field coils.  This works great…   as long as the motor is spinning.  From a stop it tends to get out of sync, but there is a cure!

The controller can use a quaderature encoder so the encoder can read the position of the armature at any speed.

To add an encoder to the motor I decided to try a chip amde by Austrial Microsystem AS5040.  This chip senses a magnet near the chip and calculates the position of the magnet and can generate multiple output:  PWM, binary via I2C, and quadurature!

I bought a few of the chips and built a surface mount board to hold the chip and a few LEDs to display the output.  The first two version had a few problems but the 3rd time was the charm.

 

 

Thanks to Royce for working out the process for surface mount PCBs.

 

The final version had to be small enough to fit in a depression in the end of the motor cap.  The sensor centered and the whole board insulated (clear enamel)  since this is a grease pocket

for the rear motor bearing.

 

 

 

 

The magnet is mounted to a bolt that is threaded into a tapped hole in the back end of the armature.  It took a while to the position right (it needs to be within a few millimeters of the sensor) hence the nuts and washers.

 

The cable is brought out of the motor through a small threaded hole (it was an alternate location for the grease fitting.)  The hole is filled with epoxy and the wires go to a DB9 connector.   I built a small test board that shows the quadurature signals (4 round LEDs) and the status outputs from the chip (the two rectangular LEDs)

 

 

 

 

 

The motor controller puts out 15V to power an encoder and wants A and B as well as inverted A and B signals.  The circuit includes some NPN transistors along with a voltage regulator and a few capacitors to tie it all together.  I put the schematic for both the sensor and test board on one schematic so I could make both boards at the same time.

I installed it in the car today, but still need to put a few more parts together to run it.

 

 

 

DOH!

It doesn’t work!

Ok, so the electronics work fine, it talks to the controller.

But it tops out at 256 pulses per revolution and the controller needs 1024.  It was a minor confusion between terminology.  The sensor detects 1024 positions, but to generate quaderature it uses 4 positions per pulse output.

Back to the drawing board.

 

I picked up a commercial shaft encoder on ebay for 50 that outputs 1024 PPR but it only works at 5V, so I’ll need a level shifter board and connector adapter.

Oh, yea, and I need to put the motor again, take out the old encoder, bring a shaft extension through the back grease pocket, add a grease seal and couple it to the encoder.

 

 

 

 

September 27th Meeting Minutes

A total of 14 members and 1 guest attended the meeting.

BarCampMilwaukee6 is this weekend!

If you haven’t yet, go visit their website at http://barcampmilwaukee.org/

Membership Promotion

Jason proposed that we actively engage the public and recruit new members.  He volunteered to lead a small group and make contact with people at area schools and colleges.  More to come shortly.

Jumpstart Sponsorships

Rich presented an idea to sponsor people who regularly attend meetings and help out at the space, but lack the disposable income necessary for membership.  Candidates would be eligible for two or more months of part-time or student level membership.  A fund has already been set up using donations from other members.

Jason noted that PS:One and other groups offer incentives to bring in materials, clean the space, teach classes, etc. and earn points which can be redeemed for merchandise, discounted dues, and more.  More details to come.

Doorbell Project

It was noted that Shane, a regular at the space but not quite a member, was left waiting outside in the rain last Friday without anyone to let him in.  People were in the space, but did not know he was out there.  The group discussed the need for a doorbell to alert occupants to the presence of guests waiting outside.  Ross volunteered to help build a system with a bell and lights and began working shortly after the meeting.

Electric Car Club Meeting October 9th

As usual, the Electric Car Club will be meeting on the second Sunday of the month.  Tom asked for a few volunteers to come to the space and help direct any guests that attend the meeting.  People will hang out between 10:00 AM and 4:00 PM with the meeting somewhere in the middle.  Tom noted that Ben is working to make the group an official chapter of the Electric Automobile Association.


DIY Plug-In Hybrid Car

Two summers ago, I built my own electric car. It’s a conversion of a ’96 Geo Metro from gas to electric. While I experimented with several different voltages, in the end I went with a simple 72V battery pack. Overall, it’s great, other than a rather short range.

Recently, I started finding that I was doing a lot of travel JUST A LITTLE FARTHER then I could go on a charge. One of the friends at the Makerspace had a propane generator kicking around, and said I could have it if I could fix it.

Hmmm…. Plug-In Serial Hybrid anyone?

Click the “read more” below for the rest of the story, including videos

Essentially, I fixed up the generator and mounted it, a fuel tank, and the battery charger in the cargo area of the car.
The generator makes electricity, and the charger pushes it to the batteries. The charger can NOT put out as much power as the car uses on cruising, so it’s NOT and “infinate range extender” the way the Chevy Volt is. Instead, it simply extends the range of the electric car by having the batteries deplete more slowly.

Here’s an overview video.

I made several videos as I was working on the project, and I think they explain everything better than I could explain by text.

Here are a few of those videos in chronological order.

And if those videos aren’t enough for you, check out my DIY instructions over at http://www.instructables.com/id/DIY-Plug-In-Hybrid-Car/