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[safe]

Just to be clear...

There is a difference between a "Boost Control" circuit and a "Currrent Based Throttle" circuit. They are similiar, but there are differences.

How they are alike:

1. Both circuits change what the controller receives as a signal from the throttle so that the controller is "tricked" into doing things differently.

2. Both circuits depend on information about current to decide what to tell the controller to do.

How they are different:

1. The "Boost Circuit" sets a fixed upper limit to the current flow and no matter what throttle setting it's in the current limit remains constant.

2. The "Current Based Throttle" has a continously variable current limit that starts at a maximum (which is adjustable) and reduces to zero based on the proportion of throttle opening.

Advantages:

1. The "Boost Control" has a "set it and forget it" mentality. If you want to conserve energy you simply turn down the boost control knob and the powerband will always be running efficiently. It's really ideal for someone that has gears because unless you come upon a hill that is so steep that you can't run in "efficiency mode" in first gear you should be able to get really great economy and get it without thinking.

2. The "Current Based Throttle" can run in high efficiency mode any time you are at partial throttle. When a hill presents a challenge all one has to do is open the throttle wide open and things automatically change so that the motor is in "power mode". This seems like a really good idea for a fixed gear, small motor configuration.

Disadvantages:

1. The "Boost Control" can leave you lacking power on a hill. You might find yourself constantly resetting the Boost Control knob with every hill and so it becomes more of a hassle than a benefit.

2. The "Current Based Throttle" forces the user to be very aware of their throttle usage. The natural human tendency to use more throttle tends to take over and while one might hope for improvements in efficiency it's also possible that one gets little out of it because the urge to open the throttle is that great.

Comments?

 

[safe]

About powerbands..

When the current limit is LOWERED the power peak shifts to HIGHER rpms and it "excludes" power at lower rpms. (bad for power, good for efficiency)

When the current limit is RAISED the power peak shifts to LOWER rpms and INCREASES power output.

So a "Boost Control" would make the power peak remain high in the highest efficiency state all the time. The "Current Based Throttle" shifts the power peak to LOWER rpms when the throttle is open and it shifts it to HIGHER rpms when the throttle is partially closed. So that's something to keep in mind, that the power peak is stationary in the "Boost Control" circuit and constantly moving for the "Current Based Throttle" circuit. I say this because you might try to imagine how hard it would be to get your "shift points" right on a geared machine if the powerband can be somewhere else depending on the throttle setting. The short answer... it would be really freaky... :?

 

[fechter]

With my current mode throttle circuit, you could have the maximum current limit adjustable by a control on the handlebars. I would then perform both functions you are describing.

 

[safe]

With my current mode throttle circuit, you could have the maximum current limit adjustable by a control on the handlebars. I would then perform both functions you are describing.

Not exactly though.

If you lower the setting for the upper amp limit your "Current Based Throttle" is STILL going to reduce the current even below what that already low limit would allow.

Let me do some numbers:

40 Amp Controller - "Boost Control" set to 20 Amps - Throttle setting is 1/4 throttle - Final current limit to the controller is 5 Amps. (when one would prefer a limit of 20 Amps even if it doesn't need it)

I suppose as long as you are always at full throttle it does become the same. but at less than full throttle you get an "amplification effect" where things drop off radically. You end up with an "on off" switch.

And it's still going to screw with the powerband. People like myself with gears don't need anything more than the "Boost Control" side and in fact it would be much easier to ride with a consistant location for the power peak. How else do you know when to shift if things are moving around all the time? You have to remember that the rider needs to get used to the level of boost and the knowledge of shift points is very critical to getting the riding part down right...

 

[safe]

I want to be clear that the "Boost Control" and the "Current Based Throttle" are two separate circuits that solve different problems. It's not a "zero sum game" because they are both great ideas that serve different needs.

 

[safe]

Fechter, my question to you is how does the circuit need to be redesigned so that you get a simple "Boost Control" rather than the full "Current Based Throttle"?

My guess is that it makes the design even more minimalistic.

Comments?

 

[safe]

Just to drive the point home, here's a few charts to express the problem of trying to use the "Boost Control" concept with the "Current Based Throttle". At Half throttle with the Boost set at 50% you effectively would get only 25% of the original limit.

This is not desireable behavior...

 

[safe]

The obvious extension of the "Boost Control" idea is to integrate it into the Amp Meter. The best product idea would be to sell a packaged product that had the Amp Meter and the "Boost Control" circuit bundled into one. House everything in a tight little plastic container and simply have a few wires sticking out, some to measure the current and others to connect to the throttle. After all, the Amp Meter and the "Boost Control" are both measuring the current anyway, so they are sort of performing similiar tasks.

This way you can watch everything that is going on and tune the Amps to exactly what you want.

 

[fechter]

As long as you have a current measurment device, either a shunt or a hall sensor, it would be easy to run an ammeter. If you use wire for a shunt, calibrating the meter might be a bit tricky, but if you have a known calibrated meter to compare with, it should be no problem.

 

[safe]

As long as you have a current measurment device, either a shunt or a hall sensor, it would be easy to run an ammeter.

Yes, I know it's going to be pretty easy to do. It would be really nice to see the results of a test of the "Current Based Throttle". The "Boost Control" circuit will be almost identical, but the current limit doesn't vary by the throttle position, only by the "boost" knob setting. (pot)

Any chance you might sketch out the "Boost Control" circuit for me?

I could probably figure it out on my own, but the whole point of having smart guys on a messageboard is to share ideas and help each other. If there comes a day when these ideas become marketable I guarantee you that my interests are with my bike designs, not the circuit. I'd be more likely to be your first "customer" than a competetor.

What do you think of making these things as a side business?

Do you have any knowledge about business? Marketing? (ever worked at a bike shop or similiar type of business)

This stuff could sell itself at first with positive "word of mouth".

 

[safe]

Turbo Charger vs. Super Charger?

The difference between the "Current Based Throttle" and the "Boost Control" is the same as the difference between a Turbo Charger and a Super Charger.

In a Turbo Charger the power increases exponentially with throttle usage and so at low throttle (and low turbo speeds) you get good gas mileage but little power and at high throttle (and high turbo speeds) you get good power but poor gas mileage.

In a Super Charger you get whatever constant rate of power boost that the Super Charger is setup to deliver. This will mean that when the boost is "up" you are always using more power even if you are at low throttle settings compared to no boost. On the positive side the boost power is very predictable... you know where the powerband is going to be, but on the negative side the power is either "up" or "down" in a constant manner.

So the two ideas (in both worlds) have their merits... they are simply different in their own ways.

 

[fechter]

To answer the previous questions, here's pretty much what the boost control circuit would look like. It might need one more pot to make the adjustment range limited to useful values. Still needs a bit more fine tuning.

The second question, producing and selling these is not very probable due to lack of time. It's not what I'm really into at this point (not fun). If somebody else wants to do it, I'd help them layout the board, spec the parts, ect. And maybe ask for a small percentage of the profits.

I'm pretty occupied with my medical device stuff. Check it out:
Click Here for Link

Dang! thats a long URL. To think that spun off from some Zappy motor magnets. Wild.

 

[safe]

Fechter, I see you are trying to get back to me, but busy. (I remember the days of working hard all the time as a computer programmer, it can be rough) Looks like you were about to post a circuit board and something didn't work out and it's nowhere to be seen. Maybe later?

In the meantime, I made up a spreadsheet that makes it easy to see the differences between how the two types of circuits would behave.

 

[fechter]

You're right, I got distracted by the "day job" just at the wrong time. Here's one version, but I think there's a simpler one in another computer somewhere.

 

[safe]

It seems like this would be the easiest thing to do...

You have a small current that you get from a Hall Effect Sensor or a Shunt and from that small current you know whether to restrict the outgoing throttle voltage or to allow it to go freely. The concepts involved would be:

1. Some sort of "Boost Control" knob (pot) that says how "high" the current sensor reading should be allowed to go.

2. Some way to compare what is happening with the motor current verses what "should" be happening with the motor current.

3. Some mechanism to restrict the throttle voltage to reconcile the two.

I wish I was more knowledgable about circuits. (it's tempting me to actually learn this stuff more)

 

[fechter]

Yes, that's pretty much what the above circuit is supposed to do.
The throttle connects to the controller like normal and the circuit does nothing until the current gets up to the set point, then the circuit pulls down the throttle voltage to keep it at the limit. Increasing the throttle will not put it past the set point. Below the set point, the circuit does not change the throttle response.

Mr. Electric built a few of these (but a different schematic) for a controller that had NO current limiter. It worked out great.

 

[safe]

So the "Boost Control" idea has been done successfully. That's good to hear. I would like to see that circuit design if anyone knows where to find it. (probably lost to the old Voltage Forum) "Boost Control" seems a little simpler than the "Current Based Thorttle" because you don't have to consider the throttle position when you are establishing the current limit. Once the pot is set in the "Boost Control" circuit the current limit is constant and final.

Do you agree with the:

"Turbo Charger / Super Charger"

...analogy as a parallel to the:

"Current Based Throttle / Boost Control"

...circuits?

They seem to be the same basic principles at work.

 

[safe]

In the "monster" 1200 Watt the top current draw for peak power will be about 75 Amps. At that rate and with my battery supply setup I'm getting a calculation of about 30 minutes of wide open full throttle time before the batteries drain.

If on that machine I have "Boost Control" and can turn the current limit down to 20 Amps then my wide open full throttle runtime stretches to a full 104 minutes.

I've compared calculations to real life on my existing bike and found that in real world conditions you have the throttle wide open about half the time (other times you are braking, coasting, at partial throttle, or are running in a higher efficiency part of the powerband which uses less energy) and so the range in real life is nearly double what the "worst case scenario" suggests.

So even on the "monster" bike if I have "Boost Control" I could still get some reasonable range numbers of 30 miles or more if I try to conserve energy. (without "Boost Control" the "worse case scenario" range would be about 20 miles)

I'm not sure how I would go about calculating the effects of the "Current Based Throttle" yet because it's variable current limit feature is harder to model on a spreadsheet. Hmmmmm...

 

[fechter]

OK, here's a simplified "Boost Control", which is simply an add-on current limiter with an adjustment pot. When the voltage drop across the shunt causes the - input to go below the + input, the amp output goes low, pulling the throttle signal down.

The 10 turn pot adjusts the maximum current limit. The other pot, which would be on the handlebars or somewhere handy, would vary the limit from about zero to whatever the maximum limit is.

This circuit may be somewhat dependent on the controller configuration, but should work with most controllers.

The op-amp should ideally have a rail-to-rail output like a MAX4162 or ICL7612. I think a TL082 would work, but may not be able to pull the throttle signal all the way down.

 

[safe]

Thanks for doing this Fechter.

Are there plans for actually making one of these (or the "Current Based Throttle" version) in the near future to have a "proof of concept" to show us?

Generally it's the "pioneer" that climbs the mountain "first" and then all the "copy cats" come afterwards. I was hoping to stand in line as a "copy cat"...

 

[safe]

Wouldn't it be nice if ALL controllers came with a knob that could adjust the current limit?

This could be a GREAT product!!!

Imagine an inexpensive Chinese controller that simply had a knob that went from "Full" (whatever that might be) to "Minimum". (whatever that might be)

Just for the sake of argument let's use:

100 Amps "Full"

10 Amps "Minimum"

 

[fechter]

Yes, and it wouldn't cost much to add that feature.
I have a pretty long list of other things controllers "should" do.

I have worked with a couple of chinese manufacturers before and it's nearly impossible to get them to change their design.

That's why we have so much fun here hacking the circuits

 

[safe]

Have you ever done the modification that simply inserts a "knob" into an existing controllers circuitry? If you knew how these things worked you could "ideally" go into the controller and find the right "wire" (or whatever in the circuitboard) and basically hack into it and run the knob directly off of that.

After all, the current limit is the primary thing that determines the "power" verses "range" charactoristics of the motor.

If it takes a whole other circuit to do this (in other words if it's complicated) then you might as well do the "external" idea like "Boost Control". Doing it internally means you don't need a shunt, which is nice.

 

[safe]

The controller is the YK42-4:

 

[fechter]

It it has a current limiter, it should not take much circuitry to make the limit adjustable. Just a few resistors should do it in most cases.