On Monday I received the new beta exciter rings for the newer style RPM sensor. You may remember that the newer style RPM sensor mounts flush to the motor and would allow me to use the remaining portion of the tail shaft on the motor to mount a pulley I can use for the A/C system.
I got to work putting the new sensor in place so that I could run some tests and get some comparison numbers. I thought I'd get a new set of numbers using the old sensor first, and then switch the leads connected to the Zilla to the new sensor and test it. Last time I got readings in first gear at 10, 15, 20 and 25 mph. I wanted to do the same thing this time, but add tests in 2nd and 3rd just to get more data.
Sadly that wasn't to be. When I was putting on the new exciter ring, I knocked the cup for the old sensor that fits over the end of the tail shaft out of alignment, and didn't notice. When I went out to test, I watched the RPMs climb to about 1600 and then the tach went dead. When I got it back in the garage, I found that the magnet inside the cup had been rubbing on the side of the cup and self destructed. *Sigh*
So I took it off and started the test on the new sensor with the new ring to get some new data. Since I had the old data from the older style sensor, I could still compare those two sets. What I found was a slight deviation. At 25 mph, the old sensor reported 4300 RPM, but the new one reports 4600 RPM.
Working with the manufacturer and Ryan at EV Source, we decided to crunch some numbers to see what it really should be. Based on the size of the tires and the final drive ratio in 1st gear, the RPMs at 15 mph should be 2632. The sensor is reporting 2600. I'd say the new sensor is more accurate than the old one.
I took off the old assembly I'd built which was designed to hold both sensors in place, and mounted up the new one. Then I mounted the pulley. I don't have a belt for it yet, so I need to get that next. Then I need to take it down to an A/C shop and find out if they can build new lines for it, and more importantly, if they are willing to. I'm really worried they'll take one look under the hood and say "No way!" In any case, I'm one step closer to A/C.
Showing posts with label RPM Sensor. Show all posts
Showing posts with label RPM Sensor. Show all posts
Friday, April 2, 2010
Friday, February 19, 2010
Testing the RPM Sensors
Today, I downloaded and set up a program that John Lussmyer wrote called ZillaConfig. It's essentially a desktop application that connects to the Zilla controller and provides you with a desktop window for configuration. It's really pretty slick. If you interested, you can get it here.
But perhaps the neatest thing it does is allow you real time graph of the Zilla's output while the car is running. You can watch motor current, throttle position and lots of other things, including RPM. So, with the ZillaConfig program loaded up and running on my laptop, I set off for testing.
Loyal readers (both of you) will remember that I installed both sensors on the car a few weeks ago; however, I could only wire one up to the Zilla at a time. So first up was the older style sensor that sits on the end of the tail shaft.
I decided the best way to test would be to put the car in first gear and spin the wheels up to 10 MPH, then 15, 20 and 25, taking RPM readings at each point. Simple enough. I ran the test on the old sensor, and then swapped the leads to the Zilla and re-ran the test with the newer sensor. Here are the results:
Old Sensor
10 MPH = 1600 RPM
15 MPH = 2500 RPM
20 MPH = 3400 RPM
25 MPH = 4300 RPM
Huh, I just noticed that there's a 900 RPM difference between each entry. Anyway, here are the results of the second, or newer style sensor:
New Sensor
10 MPH = 2500 RPM
15 MPH = 3700 RPM
20 MPH = 5000 RPM
25 MPH = -
The Zilla wouldn't let me over 5000 RPM, so I couldn't get to 25 MPH. Clearly, the two sensors are not sending the same signal to the controller. Bad news for me. I need to use an RPM sensor to protect the motor from over spinning it, so doing without really isn't an option. But if the only one I can use is the older one, that means the end of the tail shaft is occupied by the sensor. That in turn means that there is no room for the pulley that I need to use to drive the A/C system. In short, old RPM sensor equals a very hot summer in the Z3.
There are a couple rays of hope on the horizon. First, the supplier that I got the sensor from is working with the manufacturer to find out what can be done, if anything, to make it work. Second, I could have a piece machined that would screw into the tail shaft and extend it by an inch or so. While not optimal, that would work.
Before I run off and have that piece made, I need to go to an A/C shop and have them look at the car and determine if it's even feasible to run the lines needed in the very cramped spot the compressor sits in. Of course I can't do that until the car is out of the garage. That tachometer can't come soon enough!
But perhaps the neatest thing it does is allow you real time graph of the Zilla's output while the car is running. You can watch motor current, throttle position and lots of other things, including RPM. So, with the ZillaConfig program loaded up and running on my laptop, I set off for testing.
Loyal readers (both of you) will remember that I installed both sensors on the car a few weeks ago; however, I could only wire one up to the Zilla at a time. So first up was the older style sensor that sits on the end of the tail shaft.
I decided the best way to test would be to put the car in first gear and spin the wheels up to 10 MPH, then 15, 20 and 25, taking RPM readings at each point. Simple enough. I ran the test on the old sensor, and then swapped the leads to the Zilla and re-ran the test with the newer sensor. Here are the results:
Old Sensor
10 MPH = 1600 RPM
15 MPH = 2500 RPM
20 MPH = 3400 RPM
25 MPH = 4300 RPM
Huh, I just noticed that there's a 900 RPM difference between each entry. Anyway, here are the results of the second, or newer style sensor:
New Sensor
10 MPH = 2500 RPM
15 MPH = 3700 RPM
20 MPH = 5000 RPM
25 MPH = -
The Zilla wouldn't let me over 5000 RPM, so I couldn't get to 25 MPH. Clearly, the two sensors are not sending the same signal to the controller. Bad news for me. I need to use an RPM sensor to protect the motor from over spinning it, so doing without really isn't an option. But if the only one I can use is the older one, that means the end of the tail shaft is occupied by the sensor. That in turn means that there is no room for the pulley that I need to use to drive the A/C system. In short, old RPM sensor equals a very hot summer in the Z3.
There are a couple rays of hope on the horizon. First, the supplier that I got the sensor from is working with the manufacturer to find out what can be done, if anything, to make it work. Second, I could have a piece machined that would screw into the tail shaft and extend it by an inch or so. While not optimal, that would work.
Before I run off and have that piece made, I need to go to an A/C shop and have them look at the car and determine if it's even feasible to run the lines needed in the very cramped spot the compressor sits in. Of course I can't do that until the car is out of the garage. That tachometer can't come soon enough!
Thursday, February 4, 2010
RPM Sensor Mount
Yesterday I finished fabricating the mount for the two RPM sensors. Regular readers will remember that the older style sensor is guaranteed to work with the Zilla controller, but it interferes with my ability to use the tail shaft of the motor to run the A/C compressor. The newer one will allow me to use the tail shaft, but has never been tried with the Zilla. I'm going to find out if it will work.
This is a side shot of the motor's tail shaft with the RPM sensors attached. On the right hand side, closest to the motor you can see the sensor with the wires protruding toward the camera. that ring just in front of it is the exciter ring mounted on the shaft of the motor. You can see that the rest of the shaft would be free if the second, older style sensor were not mounted over the end of the shaft, which you can see on the left. It has a little black cup (which you can see) mounted over a magnet (which you can't see) that is screwed onto the end of the tail shaft. The whole point of having both mounted at the same time is so that once I get the motor spinning, I can simply swap which leads are attached to the controller and monitor the output from each.
The controller expects four pulses per revolution, which each sensor can do. I don't expect there will be a problem with either, but I'm really hoping the newer style one works, or it's no A/C for me!
I must have an RPM sensor on the motor. The motor's red line is 5500 RPM. It will tolerate higher speeds for short times, but not for sustained periods. The danger is that the all the copper in the motor will unwind off of the armature, thus destroying the motor. The controller has a feature that will allow me to set a red line that the controller simply won't pass. Of course I have to be careful and not drop the car in the wrong gear and over spin the motor. You can also set the controller so that it limits the RPM to a much lower number when the car is in reverse. That should be handy. But one of the coolest features is called Valet mode. All I have to do is press a button (yet to be installed) and it tells the controller to put it in Valet mode. I can set that up so that the controller limits current and RPM of the motor. Essentially keeping someone who isn't used to the car (a valet, mechanic, or teenager) from taking off like a nut.
After I finished that I got to work on the large battery box up front. I managed to get the brackets made and half the batteries installed and fastened down.
That was exceedingly difficult, the spaces are very tight. Notice that gap between the top of the battery on the right hand side and the bracket? I'll be shimming that somehow. You'll also notice that the terminals on the batteries are facing each other, which probably alarms the more astute readers. If they were to touch... It's kind of like crossing the streams. you don't want to allow that to happen. Well the brackets won't allow them to move closer than they are toward each other. But to be certain, I'll be placing some non conductive material between them just to be sure.
Today I had planned on finishing the battery installation on this box, but it looks like that's going to have to wait. I'm under doctor's orders not to lift anything heavy for two weeks. *Sigh* The other day I pinched a nerve in my neck and lost all feeling in my left arm. I can assure you that was a bit scary. But all is well. The Dr. has put me on anti-inflammatory medication and want's me to take it easy for two weeks. I'm sure lifting one battery at a time isn't a problem, but wrestling with stacks of 4 is probably not wise. I think progress will slow for a while. I'm going to see how much other stuff I can get done in the mean time.
This is a side shot of the motor's tail shaft with the RPM sensors attached. On the right hand side, closest to the motor you can see the sensor with the wires protruding toward the camera. that ring just in front of it is the exciter ring mounted on the shaft of the motor. You can see that the rest of the shaft would be free if the second, older style sensor were not mounted over the end of the shaft, which you can see on the left. It has a little black cup (which you can see) mounted over a magnet (which you can't see) that is screwed onto the end of the tail shaft. The whole point of having both mounted at the same time is so that once I get the motor spinning, I can simply swap which leads are attached to the controller and monitor the output from each.The controller expects four pulses per revolution, which each sensor can do. I don't expect there will be a problem with either, but I'm really hoping the newer style one works, or it's no A/C for me!
I must have an RPM sensor on the motor. The motor's red line is 5500 RPM. It will tolerate higher speeds for short times, but not for sustained periods. The danger is that the all the copper in the motor will unwind off of the armature, thus destroying the motor. The controller has a feature that will allow me to set a red line that the controller simply won't pass. Of course I have to be careful and not drop the car in the wrong gear and over spin the motor. You can also set the controller so that it limits the RPM to a much lower number when the car is in reverse. That should be handy. But one of the coolest features is called Valet mode. All I have to do is press a button (yet to be installed) and it tells the controller to put it in Valet mode. I can set that up so that the controller limits current and RPM of the motor. Essentially keeping someone who isn't used to the car (a valet, mechanic, or teenager) from taking off like a nut.
After I finished that I got to work on the large battery box up front. I managed to get the brackets made and half the batteries installed and fastened down.
That was exceedingly difficult, the spaces are very tight. Notice that gap between the top of the battery on the right hand side and the bracket? I'll be shimming that somehow. You'll also notice that the terminals on the batteries are facing each other, which probably alarms the more astute readers. If they were to touch... It's kind of like crossing the streams. you don't want to allow that to happen. Well the brackets won't allow them to move closer than they are toward each other. But to be certain, I'll be placing some non conductive material between them just to be sure.Today I had planned on finishing the battery installation on this box, but it looks like that's going to have to wait. I'm under doctor's orders not to lift anything heavy for two weeks. *Sigh* The other day I pinched a nerve in my neck and lost all feeling in my left arm. I can assure you that was a bit scary. But all is well. The Dr. has put me on anti-inflammatory medication and want's me to take it easy for two weeks. I'm sure lifting one battery at a time isn't a problem, but wrestling with stacks of 4 is probably not wise. I think progress will slow for a while. I'm going to see how much other stuff I can get done in the mean time.
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