Running high current electric solenoid using a H-bridge

[Jimbo bob]

@Jimbo bob: Okay, what ARE you trying to DO? Do you ride a motorcycle? If so, what is the year, make, and model? Are you disabled and incapable of foot-shifting? Are you trying to help a disabled person who wants to ride? Do you want to power-shift with the clutch engaged by interrupting the ignition? Do you race? Please tell us what the end-game is, as I see this thread going nowhere without specific hardware goals.

You posted a video showing a Kliktronic Gear Change on a Honda Deauville crotch-rocket that basically started from N, down-shifted to 1 and then ran up through the gears to 5 and then down-shifted back down to 1 before finally up-shifting into N. That last "shift" to N was accomplished with a short-pulse to up-shift from 1 to N (basically taking it out of gear) without enough impulse to push the shift lever through the N position to 2nd gear.

This is all very familiar to a rider who shifts with their left foot. You soon get a "feel" for how much boot action is required to up-shift from 1st gear into neutral. Down shifting is a similar feeling, but I usually overshot the N position and wound up in 1st gear if N was where I wanted to be... like when idling at a long stop with the clutch lever released. Or sometimes I would hit N while aiming for 1st and forget it was still in N when the light changed to green. Another embarrassing senior moment, especially if riding with friends. So, upon stopping, I would down-shift repeatedly to make sure I was in 1st gear. You can't go any lower than 1st, but there is no harm in making sure you really are there before trying to move again.

All of that applies to modern motorcycles. The earlier ones had different arrangements for clutch and shift levers. We won't go there. Modern shift levers have a spring-return to a "center position" that is moved to either side of center to shift gears up and down. The foot lever is lifted up with toe of the boot to up-shift and pressed downward to down-shift. Neutral (all gears disengaged) is between 1st gear and 2nd gear. This is why a solenoid actuator has to be free-floating when attached to the gear lever. It must allow the gear lever to return to its spring-loaded center position between shifts. Note in the video that the solenoid also pivots slightly to accommodate the arc through which the shift lever moves. It makes almost no sense to me that you would want the shift lever to ever assume and hold a half-shift position when shifting into neutral from either 1st gear or 2nd gear. What you want it to do is disengage either 1st gear or 2nd gear without moving far enough to engage the next gear whether up-shifting or down-shifting. That only requires a short impulse from the solenoid armature (what you are calling the piston) instead of a steady sustained shove which occurs if the solenoid stays energized.

I suppose you could add a third shift button, to be used only to shift from 1st to N or from 2nd to N, and you possibly could gin up something (maybe a third or fourth coil?) to make the shift lever move to a so-called half-shift point and stay there until you released the third button. Note there would be two "half-shift" positions corresponding to shift up from 1st to N and shift down from 2nd to N. Heck, we could get even more fancy and add electronics that would "find" N from any gear! But for me, that ain't what MC riding is about. Wind in your face, an open road with some spiffy curves, a friend on the back, and a full tank of gas that didn't require a second mortgage... that's what MC riding is to me. I don't spend a whole lot of time trying to find Neutral gear.

Hop

Okay, what ARE you trying to DO?

Hi,

I apologize for sounding all over the place. Please let me know if it is still unclear what I am trying to do by the end of this post.

Do you ride a motorcycle?

No.

What is the year, make, and model?

The engine of interest is a Yamaha R6 600cc engine which is off of a motorcycle. I do not know the make, model and the year of the motorcycle which it is from. The platform of interest is a car.

Are you disabled and incapable of foot-shifting?

No.

Are you trying to help a disabled person who wants to ride?

No.

Do you want to power-shift with the clutch engaged by interrupting the ignition? Do you race?

I personally do not race, but yes, the idea is to be able to use ignition cut to change gears while the car is in motion and use a mechanical clutch when the car is stationary. Meanwhile, in both cases an actuator (like a solenoid) will do the moving of the gear lever.

It makes almost no sense to me that you would want the shift lever to ever assume and hold a half-shift position when shifting into neutral from either 1st gear or 2nd gear. What you want it to do is disengage either 1st gear or 2nd gear without moving far enough to engage the next gear whether up-shifting or down-shifting. That only requires a short impulse from the solenoid armature (what you are calling the piston) instead of a steady sustained shove which occurs if the solenoid stays energized.

YES!! I do not want the armature to hold a position, but rather disengage either 1st gear or 2nd gear without moving far enough to engage the next gear whether up-shifting or down-shifting.

Heck, we could get even more fancy and add electronics that would "find" N from any gear!

I will be also looking into that. But it is not the priority now. First, I just want to lock-in the actuator. Then I just want to look into the electronics to control it which we have already talked about.

The Klictronic solenoid turned out to be quite expensive, so I am looking cheaper alternatives. Based on what we have discussed (and please correct me if I am wrong), a single coil solenoid will result in unequal push/pull forces and if I am using them, I will be needing two for each direction or just find a solenoid with two coils (Any alternative and better methods or actuators in mind will be appreciated).

For finding the “half-shift” do you recon feeding back the gear sensor readings to a control circuitry of some sort and feed the current to the solenoid based on that? If I am going to do it this way I have to mindful of the solenoid’s duty cycle I believe, so I would not keep it on for longer than necessary. I would appreciate it if you let me know of any other ideas which you think might work better.

Thanks for bearing with me by the way, I know I tend to get confused and go all over the place now and then.

 

[hevans1944]

Your reply about this being a motorcycle engine and transmission fitted for an automobile got me to thinking that maybe two conventional solenoids with free-floating armatures mounted on opposite sides of the shifting lever might work. In the de-energized position, the spring-return to center action of the shift lever would hold both solenoid armatures away from their respective actuated positions. When you energize one solenoid, its coil would pull its armature in to change gears. One solenoid does the down-shifting and the other does the up-shifting. Of course you would never energize both solenoids at the same time to change gears, since they pull (or push) on the shift lever from opposing directions, but perhaps some sort of pulsed operation of both solenoid coils simultaneously could aid in "finding neutral"? Experimentation needed.

Here is a solenoid with two coils, one for pulling (or pushing, your choice of either depending on which end of the armature you attach the load) with high current at high force initially produced by the primary coil, and a secondary (presumably lower current) coil for holding position when the primary coil is de-energized. However, I don't see why you couldn't do the same thing by simply reducing the primary coil current after the armature has moved. What I like about this solenoid is the boot to protect the push rod from the elements. The pulling end with the 1/4-28 threaded rod has no boot, but you probably wouldn't be using that end. I would suggest purchasing two of these, mounting them on opposite sides of the shift lever, and then experimenting to see how much to pulse each coil to produce the shifting and "half-shifting" effect you want.

I am not familiar with "gear sensor readings" vis a vis motorcycle transmissions. How does that work? Is it a retrofit to an existing transmission? What sensors are used?

Based on what we have discussed (and please correct me if I am wrong), a single coil solenoid will result in unequal push/pull forces and if I am using them, I will be needing two for each direction or just find a solenoid with two coils (Any alternative and better methods or actuators in mind will be appreciated).

Correct, a single solenoid will produce a force that increases as the armature moves toward the energized position, reaching its maximum when the armature is either fully inserted within the coil or hard-up against the solenoid magnetic pole-piece if such an arrangement is provided. So, given the uni-directional nature of the magnetic force created by the current in the solenoid coil, two solenoids or a solenoid with two coils (the Kliktronic approach) is needed for bi-directional force application without spring restoration to a de-energized position. I am not a big fan of using springs with solenoid actuators to return the actuator to a de-energized position, but some mechanical designs seem to require it. Springs mean you need additional energy to stretch or compress the spring when the solenoid coil is energized. Although that energy is stored in the spring as mechanical energy, in practice you never get it back electrically. Mechanical design strays far from the path of electrical design, although similar engineering principles apply. The marriage of the two is called mechatronics and is quite the upcoming new profession. So good luck with that. BTW, I and other electrical engineers have been quietly doing mechatronics (without the fancy name) for many years, often with backup or coordination from engineers of other disciplines.

 

[Jimbo bob]

Your reply about this being a motorcycle engine and transmission fitted for an automobile got me to thinking that maybe two conventional solenoids with free-floating armatures mounted on opposite sides of the shifting lever might work. In the de-energized position, the spring-return to center action of the shift lever would hold both solenoid armatures away from their respective actuated positions. When you energize one solenoid, its coil would pull its armature in to change gears. One solenoid does the down-shifting and the other does the up-shifting. Of course you would never energize both solenoids at the same time to change gears, since they pull (or push) on the shift lever from opposing directions, but perhaps some sort of pulsed operation of both solenoid coils simultaneously could aid in "finding neutral"? Experimentation needed.

Here is a solenoid with two coils, one for pulling (or pushing, your choice of either depending on which end of the armature you attach the load) with high current at high force initially produced by the primary coil, and a secondary (presumably lower current) coil for holding position when the primary coil is de-energized. However, I don't see why you couldn't do the same thing by simply reducing the primary coil current after the armature has moved. What I like about this solenoid is the boot to protect the push rod from the elements. The pulling end with the 1/4-28 threaded rod has no boot, but you probably wouldn't be using that end. I would suggest purchasing two of these, mounting them on opposite sides of the shift lever, and then experimenting to see how much to pulse each coil to produce the shifting and "half-shifting" effect you want.

I am not familiar with "gear sensor readings" vis a vis motorcycle transmissions. How does that work? Is it a retrofit to an existing transmission? What sensors are used?


Correct, a single solenoid will produce a force that increases as the armature moves toward the energized position, reaching its maximum when the armature is either fully inserted within the coil or hard-up against the solenoid magnetic pole-piece if such an arrangement is provided. So, given the uni-directional nature of the magnetic force created by the current in the solenoid coil, two solenoids or a solenoid with two coils (the Kliktronic approach) is needed for bi-directional force application without spring restoration to a de-energized position. I am not a big fan of using springs with solenoid actuators to return the actuator to a de-energized position, but some mechanical designs seem to require it. Springs mean you need additional energy to stretch or compress the spring when the solenoid coil is energized. Although that energy is stored in the spring as mechanical energy, in practice you never get it back electrically. Mechanical design strays far from the path of electrical design, although similar engineering principles apply. The marriage of the two is called mechatronics and is quite the upcoming new profession. So good luck with that. BTW, I and other electrical engineers have been quietly doing mechatronics (without the fancy name) for many years, often with backup or coordination from engineers of other disciplines.

Hi there,
Thanks for the reply.

[QUOTEI am not familiar with "gear sensor readings" vis a vis motorcycle transmissions. How does that work? Is it a retrofit to an existing transmission? What sensors are used?][/QUOTE]
Here are some examples that I had in mind down below, but for now, I will only try to get the system working and later work on making it "smart" in finding the neutral. So, I will not need to worry about the gear sensor feedback just yet.

There are off the shelf products which are similar to a potentiometer. They change resistance based on which gear is engaged:

http://www.aliexpress.com/store/pro...-gear-sensor-N-6-OR-0/439112_32242690112.html
Also I have seen people getting creative and use Hall sensors on the gear lever and the fact that some engines have a physical switch for the neutral. They use the neutral as a reference:
http://www.electronics-lab.com/project/motorcycle-universal-gear-indicator/
Meanwhile, I was thinking about the battery capacity and capabilities in running an instantaneous 35A-40A solenoid. In my earlier posts, I posted links to the information page of the battery that I am using, and I have been looking at its CCA(cold cranking amps) to decide whether the battery will last the solenoid as an instantaneous load or not. I just wanted to confirm with you whether I am on the right track? If I am introducing this new load (i.e. the solenoid) is there anything else (in terms of just the battery requirement) that I need to take into account so I won't damage the battery?

 

[hevans1944]

If the engine is running, the short high-current pulse sent to the solenoid will be quickly replaced by the alternator charging the battery. No worse than turning your headlights to high beam IMO. You could also consider adding a large electrolytic capacitor to store enough charge to activate the solenoid and re-charge between gear shifts, but I don't think that will be necessary, especially if you size the wires big enough to handle the current without a significant voltage drop in the wire.

The after-market gear change/gear position indicators are interesting, but the one shown in the video is not very informative. It looks like some sort of index switch that is rotated back and forth by the gear shift lever, perhaps selecting different resistor values for use in a display, but this is just speculation. The DIY device must have a "NEUTRAL" switch so it doesn't "get lost" counting up and down through the gear shifts. Nice software feature that it automatically resets if the shifter is placed in neutral.