Paul & Sabrina's cheap DIY 144v motor controller

[esoneson]

Paul, Roger, et al,

While you are thinking about getting a PCB put together, please try and include an RS232 DB9 connector and MAX232 chip to connect to the Tx Rx of the atmega16.
This will be VERY useful for both the 144volt controller and Rogers air conditioning motor controller.

Here is a site that shows the very schematic and........tadah!.......source code to use for input and output. Have a look. It is very simple and straight forward, right up our alley!

http://www.captain.at/electronic-atm...erial-port.php

Thanks guys, really looking good.

Eric (and don't forget mosfets Jake and Emma)

[NiHaoMike]

Originally Posted by Intrigued

HUH??? Am I getting too old school here? I've never met a car that had a direct drive A/C. What do they drive it off of, the timing chain???

Modern compressors have the motor directly turning the compressor. In fact, most modern compressors have the motor and actual compressor permanently welded together in a box (hermetic compressor). It is cheaper to weld the parts together than it is to make a leak-tight seal with bolted pieces, so bolted construction (serviceable compressor) is only used when serviceability outweighs the extra cost.

But since it appears that we're dealing with an old serviceable compressor originally designed for belt drive (can you please show a picture to clarify?), is there a way to remove the pulley and fit a coupler to directly connect it to the motor? In particular, belt drive would be a bad idea for a brushed DC motor. If the belt breaks, the motor would spin too fast and possibly burn out unless there's a protection circuit. (In contrast, a brushless DC or AC motor would just harmlessly run without a load.) I suppose you could glue some magnets to the motor pulley and use a pickup coil to detect the motor speed. If it exceeds a limit, power off the motor. (That'll also allow for PLL-type control of motor speed.)

They were going on about how these compressors would use so much less horsepower when it wasn't needed, to help with fuel economy. This was about 20 years ago, so I'm guessing they've come up with more efficient compressors...

The most common compressor used today is the scroll compressor. Copeland is the leading manufacturer of scroll compressors.

[Roger Heuckeroth]

Mike,

The 3:1 reduction is to multiply torque. If I had a motor that was low RPM high torque, then I would direct couple the motor to the compressor. However, I got this motor surplus for $50 and said to my self, "I can make this work." New this motor is like $1,000. If I were to source a special motor for direct drive it would be even more. So, you work with what you have.

Good comment on the speed. Paul, can we have overspeed sensor tie in on this controller?

Roger

[NiHaoMike]

Originally Posted by Roger Heuckeroth

Mike,

The 3:1 reduction is to multiply torque. If I had a motor that was low RPM high torque, then I would direct couple the motor to the compressor. However, I got this motor surplus for $50 and said to my self, "I can make this work." New this motor is like $1,000. If I were to source a special motor for direct drive it would be even more. So, you work with what you have.

Good comment on the speed. Paul, can we have overspeed sensor tie in on this controller?

Roger

A more reliable way to do it might be to use gears or chains. Less likely to break.

[GrahamMc]

If you can get a Circuit board schematic together for Futurelec and a components list for what you have with the more obvious upgrades, I will buy it all and take pictures as I go to put together a manual. Maybe even some digital video?

Now, does anyone know how I can make my own motor for $300?

[Roger Heuckeroth]

Mike,

Gears need lubrication, and both gears and chains are noisy compared to belts. I will be conservative when I size the belt. Also, in my business we manufacture air pollution control systems that often have large fans. Most of these fans run 24/7/365 and the belts last for years. I think one of the reasons that automotive belts fail quicker is the severe environment that they operate in. All that heat from the ICE makes them fail quicker, IMO.

[Roger Heuckeroth]

Graham,

If you want to get a motor for $300 your best bet is to try to find a used one on Ebay. I have heard of them going fairly cheap. Even it you need to replace the brushes and bearings, you will still be ahead. Building a motor from scratch for $300 would be next to impossible. I believe Paul got his fairly cheap.

Roger

[MPaulHolmes]

It's true! Mine was $128 on Ebay, with $16 shipping. It's only 6.7", but it still works just fine at 72v. I added a blower for another $30, and now have no heating issues whatsoever. I finished etching the power section of the second controller. I've also looked into opto-isolation. I know what parts to get, at least for the isolators. I'm not sure about the actual implementation yet. I haven't finished reading up on it yet. I also need to order 2 ATMega16's. It's always good to have a spare, for when you plug one in backwards!

[Roger Heuckeroth]

Here's a couple motors on Ebay:

Nice 9" ADC Motor Item number: 160325490924

Cheap Toyota fork lift motor Item number: 360144190989
This one would need an unusual adapter plate made.

[lectruck]

Great deal on the first motor
Advanced DC 9.1" Electric Motor - FB1-4001A- for EV - eBay (item 160325490924 end time Apr-04-09 07:21:04 PDT)


DC Motor Toyota Forklift #14120-21561-71 good used - eBay (item 360144190989 end time Apr-09-09 13:38:36 PDT)

This second one would be interesting to get an adapter plate to work.

And is there any update on the diy battery charger?