Fechter's current based throttle
- Thread starter Mathurin
- Start date
sorry, i have never followed it through any further than has already been discussed. i do remember that they use the power pin for the pwm output or something like that. if you look at the signals with a scope with the controller operating it should not be too difficult to figure out.
maybe somebody else has the drawing?
maybe somebody else has the drawing?
Fechter,
I have seen your partial diagram and also have KA3525 pdf file.
Pin 3 and 4 are also cut off in my X-controller.
I tried to trace back from pin 8 (soft-start) which is connected to the output of an comparator.
Then tried to trace back from the input of this comparator. But unable to trace where the input is connected to!
This input must be connected via "some-link" back to the throttle input.
Modification will be more meaningful if this "some-link" could be sorted out.
It will be helpful if some one could provide an schematic diag for the X-controller.
I have seen your partial diagram and also have KA3525 pdf file.
Pin 3 and 4 are also cut off in my X-controller.
I tried to trace back from pin 8 (soft-start) which is connected to the output of an comparator.
Then tried to trace back from the input of this comparator. But unable to trace where the input is connected to!
This input must be connected via "some-link" back to the throttle input.
Modification will be more meaningful if this "some-link" could be sorted out.
It will be helpful if some one could provide an schematic diag for the X-controller.
The7 said:
Indeed.
Between the throttle connector and pin 8 on the KA3525 things get quite messy on the board. There's a couple of op amps and a mess of resistors, etc. The brake switch inhibit seems to tie in there somewhere too.
Some traces run under parts so it's very hard to map out without removing some of the chips. Since my controller is working, and I want to keep it that way, I've been hesitant to desolder them.
If somebody had a "beyond repair" board, the parts could be traced out more completely.
I think it is unlikely the manufacturer would ever release a copy of the schematic.
TylerDurden
100 GW
Dermot has also indicated he could x-ray components for us...
http://endless-sphere.com/forums/viewtopic.php?p=20694&highlight=xray#20694
8)
http://endless-sphere.com/forums/viewtopic.php?p=20694&highlight=xray#20694
8)
jmfife
1 µW
fechter said:
Fechter (Richard?):
I'm that guy.
Yep; mine is digital but I wouldn't necessarily say it's a better design than yours. When you described your op-amp approach to me last year, I thought it sounded great, but I am not as proficient with analog so I stuck with the digital design (PIC16) that I had already started. Plus I wanted a progressive throttle ramp and didn't see an easy way to do that with analog.
But yours is much less complex. Really nice and simple! Very cool! And good to see you put it into practice!
Isn't is a world of difference? To me, it's like riding a new machine. I love my EV now.
I thought originally that I may be able to recoup some of my effort by selling some of these gadgets, but, the more I look at the market, the more I realize everything needs to be custom. My device, for example, currently only works with controllers that have 0-5V throttle inputs. I have been thinking of using a digital potentiometers output but since I have a full-time job and an attention-deprived kid, I have pretty much stopped work on the throttle device for the time being.
Anyway, controller manufacturers will surely start addressing the throttle feel issue soon and start building current control into their algorithms.
I am glad I checked out this forum and saw your entry because I didn't know how to get ahold of you and didn't catch you at this year's Palo Alto EV rally.
Cheers,
Mike Fife
the circuit between the throttle input and the soft start cap on pin 8 just subtracts a volt and scales the result into 0-5v so the throttle 1-4v produces 0-5v to pin 8, over-riding the charge of the soft start cap. this is done so that they can steal away the op amp meant for this purpose and use it for low voltage detection.
the ebrake input also pulls down the throttle input through a diode, before the scaling op amp.
there is a circuit triggered by the gate signal of the right (blue) channel that goes through 10k to a cap on an op amp input that drives the shutdown signal on pin 10 of the ka3525 high (1.8v) when there is no gate clock, in an attempt to shut down the pwm when the motor stalls.
the fets usually blow before this circuit can save the day in a hard stall.
the ebrake input also pulls down the throttle input through a diode, before the scaling op amp.
there is a circuit triggered by the gate signal of the right (blue) channel that goes through 10k to a cap on an op amp input that drives the shutdown signal on pin 10 of the ka3525 high (1.8v) when there is no gate clock, in an attempt to shut down the pwm when the motor stalls.
the fets usually blow before this circuit can save the day in a hard stall.
Hey Mike, glad you found the forum.
Yes, it does make the throttle response much more controllable. Really keeps the peak amps down too. I still like to bypass it frequently for maximum amp takeoffs
They really should have this feature built into all controllers :wink:
Using the Allegro hall current sensor makes it pretty simple with an analog circuit. The Allegro sensors come in various ratings, and there are ways to scale them to higher currents. The rest of the circuit would be the same, so customization is not too difficult.
Building and selling gadgets is a tough business. The EV market is still too small and, as you point out, non-standardized in many ways. The CycleAnalyst might have this feature in future software. The hardware is all there for them. That would make for pretty stiff competition.
Now if you wrote code for a full e-meter gadget like the CA, then you might have a much bigger market (especially if you can beat their price). I'm all in favor of competition if it brings the price down. I'd like to see one with bar graphs, cool backlighting, current feedback throttle, battery gauge, etc. Of course, all this should be integrated into the controller from the beginning.
Yes, it does make the throttle response much more controllable. Really keeps the peak amps down too. I still like to bypass it frequently for maximum amp takeoffs
They really should have this feature built into all controllers :wink:
Using the Allegro hall current sensor makes it pretty simple with an analog circuit. The Allegro sensors come in various ratings, and there are ways to scale them to higher currents. The rest of the circuit would be the same, so customization is not too difficult.
Building and selling gadgets is a tough business. The EV market is still too small and, as you point out, non-standardized in many ways. The CycleAnalyst might have this feature in future software. The hardware is all there for them. That would make for pretty stiff competition.
Now if you wrote code for a full e-meter gadget like the CA, then you might have a much bigger market (especially if you can beat their price). I'm all in favor of competition if it brings the price down. I'd like to see one with bar graphs, cool backlighting, current feedback throttle, battery gauge, etc. Of course, all this should be integrated into the controller from the beginning.
jmfife
1 µW
Richard:
Yes; a Hall current sensor would be great if one could be found with good bandwidth and high current range. It looks like the Allegro has plenty of bandwidth and can measure up to 200A. Not quite enough current for my bike. I have looked at a few others before with the same result. It seems like measuring high current should be easier due to the higher magnetic fluxes / Hall signal, but I have not yet found any high current sensors for a reasonable price.
I meant to ask: what is the CA? I don't think any of the features you describe are difficult from a software standpoint.
On my motorcycle, my newest controller gadget interfaces with Alltrax controllers via the serial port and pulls down parameters such as motor current, batt voltage, batt current, etc. That replaces my old system that required the current shunt. So it's shunt-less and Hall-less and has a nice backlit LCD display. Another nice thing is that I don't need to change any resistors to adjust parameters -- just reprogram. Works pretty sweet. But again only works with Alltrax controllers unfortunately.
-Mike
Yes; a Hall current sensor would be great if one could be found with good bandwidth and high current range. It looks like the Allegro has plenty of bandwidth and can measure up to 200A. Not quite enough current for my bike. I have looked at a few others before with the same result. It seems like measuring high current should be easier due to the higher magnetic fluxes / Hall signal, but I have not yet found any high current sensors for a reasonable price.
I meant to ask: what is the CA? I don't think any of the features you describe are difficult from a software standpoint.
On my motorcycle, my newest controller gadget interfaces with Alltrax controllers via the serial port and pulls down parameters such as motor current, batt voltage, batt current, etc. That replaces my old system that required the current shunt. So it's shunt-less and Hall-less and has a nice backlit LCD display. Another nice thing is that I don't need to change any resistors to adjust parameters -- just reprogram. Works pretty sweet. But again only works with Alltrax controllers unfortunately.
-Mike
doubling the current sensing capability is simple; you just split the conductor carrying the current and pass half the current through the sensor. if the connections are done carefully so that the impedance through each path is the same, there is no reason this cannot be quite accurate.
the CA is short for the cycle analyst, the latest incarnation of the drain brain,. which incorporates current and speed limiting by pulling down the throttle voltage
the CA is short for the cycle analyst, the latest incarnation of the drain brain,. which incorporates current and speed limiting by pulling down the throttle voltage
Geebee
1 kW
Which circiut is the final design? and any users out there report on how it is performing?
Cheers
Cheers
mukeshp11
10 µW
Dear All,
We have done current based throttle operation in software only.So no need of hardware for that.
Also along with it motor current control has been done with shunt in all the bottom leg of the inverter.
Also changing software is bit easy and fine.and its working fine.
Mukeshh
We have done current based throttle operation in software only.So no need of hardware for that.
Also along with it motor current control has been done with shunt in all the bottom leg of the inverter.
Also changing software is bit easy and fine.and its working fine.
Mukeshh
mukeshp11: What product are you referring to?
And I hate to bring up an old thread, but I've got the same questions as Geebee...wheres the final design?
I've actually been talking with my buddy about building a similar circuit to this, but I feel that Fetcher has redesigned this much better than we can, at least without running through all the same problems.
Im running an overvolted scooter, and while its great at 38mph, i dont have any low end speed control any more, and to try to drive with a stock one at 20mph, it destroys the batteries as im constantly jumping between accelerating and no throttle
And I hate to bring up an old thread, but I've got the same questions as Geebee...wheres the final design?
I've actually been talking with my buddy about building a similar circuit to this, but I feel that Fetcher has redesigned this much better than we can, at least without running through all the same problems.
Im running an overvolted scooter, and while its great at 38mph, i dont have any low end speed control any more, and to try to drive with a stock one at 20mph, it destroys the batteries as im constantly jumping between accelerating and no throttle
mr.electric
10 kW
I feel the need for this circuit on my BMC 1000watt hub motor and 50 amp controller. It is as if the throttle starts at 3/4 throttle. It is just a software update in controllers that allow reflash otherwise it is a circuit that must be tailored to each individual controller due to feed back issues. The Cycle Analyst 2 has a current based throttle option but it also only works on certain brands and requires some fine tuning at that. A friend tried the current based throttle on the cycle analyst on my particular controller but said he just could not get it to work despite contacting the cycle analyst creator and receiving significant support.
I would contact your controller manufacturer and ask if software can be reflashed. They will probably say no even if it is possible. On the off chance that they want to talk to you about their software they may provide you with an updated file.
This is one of those concepts that improves driveability so much it should be part of every controller.
Fetcher made a simpler current limiting throttle a few years back.
I installed it on 4 high powered currie izip scooters with 175 amp controllers. I built it from his schematic and it did the trick. The funny thing was the 4th scooter would not work right with the circuit installed. I kept thinking I had screwed up soldering the little current limiting board. Then I swaped the controller for an identical make and model and it worked!
The best part of this circuit was it limited current based on an adjustable knob but when you hit full throttle the limit disappeared. I may even try one of these circuits on my bmc.
I would contact your controller manufacturer and ask if software can be reflashed. They will probably say no even if it is possible. On the off chance that they want to talk to you about their software they may provide you with an updated file.
This is one of those concepts that improves driveability so much it should be part of every controller.
Fetcher made a simpler current limiting throttle a few years back.
I installed it on 4 high powered currie izip scooters with 175 amp controllers. I built it from his schematic and it did the trick. The funny thing was the 4th scooter would not work right with the circuit installed. I kept thinking I had screwed up soldering the little current limiting board. Then I swaped the controller for an identical make and model and it worked!
The best part of this circuit was it limited current based on an adjustable knob but when you hit full throttle the limit disappeared. I may even try one of these circuits on my bmc.
mukeshp11, I'm glad to see someone finally adopt this feature into a controller (and make it work).
While you're at it, how about a good sensorless mode and motor temperature feedback :wink:
Most of my earlier circuits were limiters and not current based throttle circuits. Making the true current mode throttle adapter work took a lot of messing around to get dialed in. I think with a bit more circuit, it's possible to make one that will cover a wide variety of controllers and not be too tricky to get set up.
I recently built a version of this for interfacing a hall effect throttle to an Alltrax controller. The design is based on the hall throttle having a 1v to 4v signal output and a 300 amp range. Current sensing is done with a LEM HASS 400-S torroidal hall effect current sensor (http://www.lemusa.com/docs/products/hass_e.pdf) At $27.50ea for the sensor, it's a spendy little bugger, but it has a hole big enough for some fat 4ga wire to pass through, which makes installation easy. This particular circuit also has an output stage that will interface to the Alltrax's 0 to 5k two wire throttle input. It also has a throttle supervisor circuit that will detect an open ground on the throttle line and kill the output (otherwise an open ground will give you full throttle).
The first prototype of this used a smaller Tamura L01Z400S05 sensor ($17.50ea) that has a smaller opening.
Here's the next version with the larger sensor opening:
Another view:
View attachment 1
The Allegro sensor would work in the same circuit, but requires cutting into a main power wire and running it through the sensor. The Allegro sensor would be perhaps better for smaller systems (under 150A)
An even cheaper approach would be to use a shunt to measure the current, but would also require inserting the circuit in line with a main power wire.
The Alltrax version was designed to be placed over a motor wire, so the current would be directly proportional to torque. In a brushless system, the motor wires are running AC and it would take a bit of extra conditioning circuitry to make it properly sense motor current. On my Vego unit, I just put the sensor in line with the battery wire (which is always DC). This results in a "power mode" rather than a "torque mode", but in actual operation it's hard to tell the difference. At low speeds, the "power mode" will give a bit higher torque for a given throttle setting.
While you're at it, how about a good sensorless mode and motor temperature feedback :wink:
Most of my earlier circuits were limiters and not current based throttle circuits. Making the true current mode throttle adapter work took a lot of messing around to get dialed in. I think with a bit more circuit, it's possible to make one that will cover a wide variety of controllers and not be too tricky to get set up.
I recently built a version of this for interfacing a hall effect throttle to an Alltrax controller. The design is based on the hall throttle having a 1v to 4v signal output and a 300 amp range. Current sensing is done with a LEM HASS 400-S torroidal hall effect current sensor (http://www.lemusa.com/docs/products/hass_e.pdf) At $27.50ea for the sensor, it's a spendy little bugger, but it has a hole big enough for some fat 4ga wire to pass through, which makes installation easy. This particular circuit also has an output stage that will interface to the Alltrax's 0 to 5k two wire throttle input. It also has a throttle supervisor circuit that will detect an open ground on the throttle line and kill the output (otherwise an open ground will give you full throttle).
The first prototype of this used a smaller Tamura L01Z400S05 sensor ($17.50ea) that has a smaller opening.
Here's the next version with the larger sensor opening:
Another view:
View attachment 1
The Allegro sensor would work in the same circuit, but requires cutting into a main power wire and running it through the sensor. The Allegro sensor would be perhaps better for smaller systems (under 150A)
An even cheaper approach would be to use a shunt to measure the current, but would also require inserting the circuit in line with a main power wire.
The Alltrax version was designed to be placed over a motor wire, so the current would be directly proportional to torque. In a brushless system, the motor wires are running AC and it would take a bit of extra conditioning circuitry to make it properly sense motor current. On my Vego unit, I just put the sensor in line with the battery wire (which is always DC). This results in a "power mode" rather than a "torque mode", but in actual operation it's hard to tell the difference. At low speeds, the "power mode" will give a bit higher torque for a given throttle setting.
OK, for the super-cheap, here's something that should work, but has not been tested.
Warning! there is no throttle supervisor, so if there is a malfunction, you could get Prius-like acceleration.
(Disclaimer
I won't be respsonsible for any injuries resulting from the use if this circuit.
Always test first with the wheel off the ground.
It's based on the OAR5R005FLF shunt resistor ($.60ea) from Mouser.
The maximum current will depend on the number of these shunt resistors you put in parallel. It should be about 20 amps per resistor, so for example, if you want a 100 amp maximum, you would use 5 in parallel. You change the maximum setting by changing the number of shunt elements. The shunt resistors can be mounted remotely and connected to the circuit by small wires if desired.
The circuit is powered off the throttle supply, so needs no separate voltage regulator.
This is intended for hall effect throttles that go from 1 to 4v.
A Rail-to-rail output op amp is recommended for this. MCP6002 or TLC2272 are possible choices. Just about any op amp with RR output should work.
VR1 gets adjusted so that the motor doesn't run when you let off the throttle.
Warning! there is no throttle supervisor, so if there is a malfunction, you could get Prius-like acceleration.
(Disclaimer
I won't be respsonsible for any injuries resulting from the use if this circuit.Always test first with the wheel off the ground.
It's based on the OAR5R005FLF shunt resistor ($.60ea) from Mouser.
The maximum current will depend on the number of these shunt resistors you put in parallel. It should be about 20 amps per resistor, so for example, if you want a 100 amp maximum, you would use 5 in parallel. You change the maximum setting by changing the number of shunt elements. The shunt resistors can be mounted remotely and connected to the circuit by small wires if desired.
The circuit is powered off the throttle supply, so needs no separate voltage regulator.
This is intended for hall effect throttles that go from 1 to 4v.
A Rail-to-rail output op amp is recommended for this. MCP6002 or TLC2272 are possible choices. Just about any op amp with RR output should work.
VR1 gets adjusted so that the motor doesn't run when you let off the throttle.
Attachments
mr.electric
10 kW
I think i'll try this one. I'll post my results within the next 18 months. Just kidding. I am going to build one as soon as possible.
@fechter:
Regarding a hall-to-pot throttle interface, a simplistic version can be done with an quad op-amp chip and a Maxim digital pot chip:
http://media.maxim-ic.com/app-notes/index.mvp/id/3284
Part of the op-amp is used to voltage scale and offset the hall voltage input, and part of it to create the oscillator to clock the digital pots.
I had a schematic drawn up for it but can't find it (was on paper that I kept meaning to scan in, but didn't).
It could probably also be used to sense and limit the current, easily enough--I had not considered that need at the time, as I was just trying to find an easy way to make a hall sensor able to control the 2QD's pot-type throttle input, and later the Curtis's which is similar, because I wanted to have chain tension on the pedal drivetrain control the motor assist. Using a pot on that would have meant figuring out a weather seal system, and extra mechanical bits, but using a hall just meant a lever with a roller on it, and a magnet on the other end, with a hall near it.
Regarding a hall-to-pot throttle interface, a simplistic version can be done with an quad op-amp chip and a Maxim digital pot chip:
http://media.maxim-ic.com/app-notes/index.mvp/id/3284
Part of the op-amp is used to voltage scale and offset the hall voltage input, and part of it to create the oscillator to clock the digital pots.
I had a schematic drawn up for it but can't find it (was on paper that I kept meaning to scan in, but didn't).
It could probably also be used to sense and limit the current, easily enough--I had not considered that need at the time, as I was just trying to find an easy way to make a hall sensor able to control the 2QD's pot-type throttle input, and later the Curtis's which is similar, because I wanted to have chain tension on the pedal drivetrain control the motor assist. Using a pot on that would have meant figuring out a weather seal system, and extra mechanical bits, but using a hall just meant a lever with a roller on it, and a magnet on the other end, with a hall near it.
Interesting app note.
My approach was pretty simple where I just used the output of an op-amp and scaled to a 0 - 3v output, which is the range that the Alltrax is looking for in the 0 - 5K mode. When the throttle input on the Alltrax goes over about 4v, it triggers the open circuit safety and shuts down the output.
I suspect the Curtis works similarly, but I don't know what the input voltage range is on one of those. If somebody could measure the throttle input voltage (against battery neg) over the full range of throttle, I could tell from that.
One of the main reasons for making this is apparently the popular Magura 5k pot throttle has a nearly 100% failure rate if used long enough. It seems the pot wiper wears through the resistor material over time.
My approach was pretty simple where I just used the output of an op-amp and scaled to a 0 - 3v output, which is the range that the Alltrax is looking for in the 0 - 5K mode. When the throttle input on the Alltrax goes over about 4v, it triggers the open circuit safety and shuts down the output.
I suspect the Curtis works similarly, but I don't know what the input voltage range is on one of those. If somebody could measure the throttle input voltage (against battery neg) over the full range of throttle, I could tell from that.
One of the main reasons for making this is apparently the popular Magura 5k pot throttle has a nearly 100% failure rate if used long enough. It seems the pot wiper wears through the resistor material over time.
Malcolm
10 kW
Richard, are you planning to build and sell the Alltrax throttle interface? If so, please put me down for one. I've learned my limitations when it comes to building electronics...
I'd also appreciate anyone's recommendations for a well-built hall throttle – suitable for motorcycle use.
I'd also appreciate anyone's recommendations for a well-built hall throttle – suitable for motorcycle use.
This looks like the same throttle I evaluated:
http://www.newkellycontroller.com/product_info.php?products_id=134
It's one of the better ones I've seen but it's still kind of cheap. Making it waterproof is fairly easy as there is a small cover over the hall sensor wire connection that can be removed so you can seal the connections (epoxy?) It has a nice machined aluminum clamp to hold it onto the handlebars.
I wasn't planning to go into production on these. The boards are very expensive if only a few are made. The sensor is dang expensive too, and the rest of the parts are about $15. I suppose if there is enough demand, I could do a run of boards. I just don't have time to build them these days. I'll keep you in mind if I wind up with a left over prototype.
http://www.newkellycontroller.com/product_info.php?products_id=134
It's one of the better ones I've seen but it's still kind of cheap. Making it waterproof is fairly easy as there is a small cover over the hall sensor wire connection that can be removed so you can seal the connections (epoxy?) It has a nice machined aluminum clamp to hold it onto the handlebars.
I wasn't planning to go into production on these. The boards are very expensive if only a few are made. The sensor is dang expensive too, and the rest of the parts are about $15. I suppose if there is enough demand, I could do a run of boards. I just don't have time to build them these days. I'll keep you in mind if I wind up with a left over prototype.
Malcolm
10 kW
I understand completely that building a few boards like this isn't really worthwhile. Many thanks anyway for publishing your circuit, and thanks for the tip on the throttle. If you do end up with a spare prototype please let me know.
Malcolm
Malcolm
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