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.





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.





Solid Wood computer desk for less than a Wallmart flat pack!

David (high school student) member of the space needs a new computer desk and wants to build it himself.

He drew up a design that is small (he lives in an apartment), can hold his new computer and monitor (big gamer case and wide screen monitor), and something he could customize.

His design is similar to what you can buy as flat pack furniture from places like Walmart for under $100:

But we want to build something that will last, something he can take to college, something strong and useful.

Here is David’s original design:

So the question is what to make it out of.

Since the desk is only 24″ deep, we could make it out of 1×12 oak boards, except that would cost over $300 for the wood!

We could make it out of plywood then go back and trim the edges with solid oak, At $40 per sheet plus the banding its going to be around $100.

Then it hit me, the desk worked out to about 55 square feet and flooring is sold by the square foot!

You can buy unfinished oak flooring for under $1.50 on sale!

After thinking about it for a while I realized the following:

Not much waste –  since you only build the boards where you need them, not cut them out of a 4×8 sheet.

Mortise and Tenon construction – just leave a board long for a tenon and a gap between planks for a mortise.

Artistic potential – you can create opening and patterns just be leaving gaps in the planks.

A visit to a few local hard wood flooring suppliers and we found a left over batch of prefinished hickory for $0.50 per square foot!

Total cost for the wood:  $28!

We picked up the wood the week before Xmas and got started Xmas eve.

Less than a week later we had the first 3 panels cut and glued and they fit together the first time!

Will it go round in circles….

What do you do when you need pictures of a 300lb power wheels car from multiple angles so that someone can create a 3D model?

You build a turn table, a rather big turn table.

But what if I don’t have a really big bearing, you ask.

Well, you use a bunch of little ones – preferably in casters!

This is a metal base with 4 casters from some old equipment that was trash, I drilled a hole in the center and welded a 1/2″ nut to the bottom.





Take 4×4 sheet of plywood, drill a hole in the center.  Just because its a quick and dirty project I put a 1/4″ thick washer under the board and figured the weight of the rig would hold it in place





Put it all together and you have a turn table that can support the Little Pink Trike and we are ready for the photo shoot!












Spinning Little Pink Trike Video on Flickr




Library of Images of the Little Pink Trike on Flickr




Electric Neon – home brew Electric car

I have been working on building an electric car for the past year.  The car is on the road and drivable.  I am starting this blog a little late so I will spend some time trying to walk through some of the early decisionis and processes. 

You can find a number of videos on youtube:

I have wanted to build my own electric car for over 20 years, it has taken that long for me to accumulate the knowledge and skills to attempt the project.  It also took a little luck to get me started.

I wanted to something a little different than what most people do, I also didn’t want to build an electric car with $20,000 worth of parts.  The original ideal was to build a car using off the shelf industrial parts:  An AC motor, an inverter (AC Drive) and available batteries.

You can find AC motors of almost any size at surplus outlets, auctions and junk yards.

The controllers are a little harder but still available and getting cheaper.

Most people use DC motors and high currents.  Using an AC motor and a battery pack that runs the equivelent of 240V AC (340V DC) means the current , and wire size, will be smaller.

What finally kicked off the project was a load of batteries showed up at work and were mine to play with.  they were C&D 12-270  UPS batteries rated at 12V  75AH.  These are rather small for a DC car (you usually want something over 200AH) but ideal to make a high voltage AC Car (12V batteries mean half as many batteries as with 6V)

I got 18 of the batteries and decided it was time to build a car.  I started out with some initial test using a 5HP motor, 5HP AC Drive and 9 13AH 12V batteries I had from the battle bots I built to see if I could run an AC motor from a battery pack.  It worked great!

Now I needed a car.  I didn’t have anything in mind so I started doing some reading and looking around.  Lighter is definitely better for electric cars, but you also need enough room and strength to hold the extra weight of the batteries (and the driver – I’m 6’4″ tall)

I have a PT Cruiser and though it would make a good electric until I saw the curb weight (over 3000 lb) but that started me looking at the Neons (built on the same chassis.)

I soon found out that the 1st generation Neons tended to be lighter (2400 lb curb weight) and they have a version with beefed up suspension  the ACR.  The ACR is a stripped down car – no extras, has 4 wheel disk brakes (all the better to stop all those batteries) and stronger suspension.  The ideal car for an electric conversion.

I found a 1999 Dodge Neon ACR on craigs list for $1200, when I went to pick it up there were 8 other Neons in the driveway!  The seller was a neon nut (I mean that in the nicest of terms) and was interested in my plan, he even bought the engine back later along with the other parts I didn’t need and has been invaluable with advice and parts, thanks Barry!