Re: Alternative Motor Speed Sensor
I don't think that the rpm specs will be an issue,
from the figures I've seen on this group each 1k rpm from the motor gets you about 7 mph, so we aren't going to be anywhere near the 18k motor spec...
Axial play in the motor will still be a concern, you will need to make sure sure your bearings are in good shape just like with the optical, but so far the amt102 seems pretty hardy and in the event that the encoder is destroyed they can be sourced through digikey for under $30, and the mounting bracket/shaft adapter shouldn't
cost much to replace either if those were to be damaged, I'm hoping to get access to a 3d printer so that I can come up with something better, will keep the group updated on my progress.
---In firstname.lastname@example.org, Gordon Stallings <gordonstallings@...> wrote:
> What a great project! The Solectria pulse tach has always been a weak
> point in their design.
> I've got a couple of questions:
> * The RPM limit in the spec sheet is lower than the top speed of the
> motor (18,000RPM). Is this a problem?
> * The specs say axial play of .3mm. Is this a problem when connected
> to the motor? Some people have mentioned that their original pulse
> tach was damaged when wear in the motor allowed too much end play in
> the motor shaft.
> On Jul 18, 2013, at 11:39 PM, Sean K wrote:
> > So some of you know that I've been working on coming up with an easy
> > replacement for the Solectria motor speed sensor for a while now.
> > I've had some pretty promising results with my most recent attempt,
> > enough so that I thought I'd share with the rest of the class (pics
> > in the Photos section)in case anyone is interested. Keep in mind so
> > far I have only driven about a mile at 15mph (i think my batteries
> > are starting to go on me)
> > So here's what I've done:
> > I got my hands on this little CUI AMT102 Capacitive Encoder (http://www.cui.com/product/resource/amt10x.pdf
> > ) as well as what they call a line driver cable although it's really
> > a Push-Pull CUI-102E-10 (http://www.cui.com/product/resource/cui-102e-10.pdf)Oh
> > and it's programmable, has a dip switch setting for 48 pulses! YAY!
> > I designed and convinced the keeper of the 3d printer at work to
> > print an a shaft adapter because the AMT102 is meant to attach to a
> > motor with a much smaller shaft.
> > Drilled a few holes in a piece of flat aluminum bar to use as a
> > mounting bracket and have the plastic bracket for the encoder taped
> > to that, yes it's a bit okie rigged, just a temporary setup,
> > eventually I want to 3D print a bracket that the encoder will just
> > clip into.
> > Removed some of the jacket from the line driver cable so that I
> > could steal the index lines X/-X (blue and white blue) to use for
> > the temperature sensor, soldered them to a little 2 pin terminal
> > block for easy no solder temp sensor connect/disconnect, also hooked
> > up an extension onto the unused cable shield to use that for ground
> > to the motor.
> > Soldered the flying leads off the line driver cable to a DB-9 Male
> > using the normal pinout, however in the 6v line I soldered a low
> > dropout regulator L4931CZ50-AP(http://www.st.com/web/en/resource/technical/document/datasheet/CD00000971.pdf
> > ) to bring the 6v down to something that wont fry the encoder.
> > I've got it all hooked up, get a good solid 5 volts on each of the
> > A/-A/B/-B lines, in the AMC program the controller shows nice pretty
> > regular motor speed readings, no jumping around like I got with my
> > old and busted optical encoder.
> > And that's about it, like I said I was able to get the car to drive
> > with it, but was maxed out at 15mph and towards the end of the 1
> > mile run was barely making 6mph so I am also pretty sure that I've
> > got some bad batteries in my pack, unfortunately the laptop I've got
> > for amcmon also has a bad pack so I can't see what the pack voltage
> > is at while I'm driving. I do notice that while i see 151 volts on
> > the big connector going to the controller, and sitting in the
> > driveway the controller says the pack is at 150 volts, as soon as I
> > turn on the headlights it drops to under 148, so I'm assuming that
> > when I try to pull enough amps to move the car the pack voltage
> > drops down even lower.
> > Well I apologize for the long drawn out post, was just excited
> > because this is the first time in months that I've been able to
> > drive the car a full mile without having to push it at least part of
> > the way home!
> > __._,.
> [Non-text portions of this message have been removed]