Digital Electronic throttle

[majid]

I am designing an electronic throttle control system for a go cart
and was wondering if anyone could help. I am planning on using a
stepper motor to move the throttle body, is that safe?(i heard it
would be better to use a servo but dont have one available) In the
event of the throttle being stuck open i was thinking of having a fuel
cut off solenoid to stop the fuel flow, is this a good solution, any
other ideas? I also need to take into account a whole lot of other
safety considerations such as what to do in the event of pedal
position sensor failure etc. any suggestions.

 

[Tim Wescott]

majid wrote:

I am designing an electronic throttle control system for a go cart
and was wondering if anyone could help. I am planning on using a
stepper motor to move the throttle body, is that safe?(i heard it
would be better to use a servo but dont have one available) In the
event of the throttle being stuck open i was thinking of having a fuel
cut off solenoid to stop the fuel flow, is this a good solution, any
other ideas? I also need to take into account a whole lot of other
safety considerations such as what to do in the event of pedal
position sensor failure etc. any suggestions.

Steppers have their place, but I honestly don't thing this is one of
them. They need to be "homed" each time you turn power on, they can
loose track of where they are if you try to move them too fast, they're
big for the amount of torque that they reliably produce, etc.

Servos are available at your nearest hobby shop, or by mail from a
number of RC aircraft distributors. They're easy to control -- you
could make your throttle with a 555 on the throttle and a servo on the
motor, you can get them in sizes ranging from tiny to huge, ect.

Normally I'd recommend that you use a microprocessor if things get even
vaguely complex (that's what software's _for_, after all). This system
is simple enough to not require it, but you'll have a smaller board with it.

Finally, use a kill switch. All you have to do is ground one side of
your magneto, and the motor will stop. Wire your kill switch so that it
is _entirely_ independent of any other system in the cart, and mount it
where you, and someone trying to rescue you, can get to it. If you are
going to race your cart in a sanctioned event your sanctioning body will
have some suggestions for this.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[Ben Bradley]

In sci.electronics.design, masehr2@hotmail.com (majid) wrote:

I am designing an electronic throttle control system for a go cart

I feel obliged to ask why (I suspect for R/C control, but it would
be better if you tell). Mechanical throttle linkages have worked well
for many years.

and was wondering if anyone could help. I am planning on using a
stepper motor to move the throttle body, is that safe?(i heard it
would be better to use a servo but dont have one available) In the
event of the throttle being stuck open i was thinking of having a fuel
cut off solenoid to stop the fuel flow, is this a good solution, any
other ideas? I also need to take into account a whole lot of other
safety considerations such as what to do in the event of pedal
position sensor failure etc. any suggestions.

Well, at least you're concerned about safety and possible failure
modes. I don't know if a servo would be any 'safer' than a stepper,
but the overall design will determine the safety and reliability of
this type of thing at least as much as any one component.

If you're going to do this, use a MECHANICAL linkage to cut off
fuel flow and/or stop the engine some other way, such as mechanically
shorting out the spark plug. Even with this and being told what to do,
a driver may freak out and not activate the linkage if something goes
wrong.
If this is for remote or radio control, have the thing turn off the
engine AND apply brakes if either the controlling signal is lost, or
battery power cuts out (have a solenoid that holds the brakes off and
lets the engine run while it has power, but a spring return causes
everything to stop if power is lost).

I do NOT have a P.E., this post is for Entertainment Purposes Only,
YMMV, HTH, HAND, yadda yadda bla bla bla, etc.

 

[Martin Riddle]

The Chevy Corvette is a drive by wire throttle. You might want to google for more info.

Cheers
"majid" <masehr2@hotmail.com> wrote in message news:76a9d499.0404280937.5f33d3ef@posting.google.com...

I am designing an electronic throttle control system for a go cart
and was wondering if anyone could help. I am planning on using a
stepper motor to move the throttle body, is that safe?(i heard it
would be better to use a servo but dont have one available) In the
event of the throttle being stuck open i was thinking of having a fuel
cut off solenoid to stop the fuel flow, is this a good solution, any
other ideas? I also need to take into account a whole lot of other
safety considerations such as what to do in the event of pedal
position sensor failure etc. any suggestions.

 

[Active8]

On 28 Apr 2004 10:37:50 -0700, majid wrote:

I am designing an electronic throttle control system for a go cart
and was wondering if anyone could help. I am planning on using a
stepper motor to move the throttle body, is that safe?(i heard it
would be better to use a servo but dont have one available) In the
event of the throttle being stuck open i was thinking of having a fuel
cut off solenoid to stop the fuel flow, is this a good solution, any
other ideas? I also need to take into account a whole lot of other
safety considerations such as what to do in the event of pedal
position sensor failure etc. any suggestions.

Another good safety mechanism is a key that attaches to your wrist.
If you wreck and are injured or freaking out, the key is likely to
pull out which would allow two contacts to make, shorting the
magneto to the block.
--
Best Regards,
Mike

 

[Rich Grise]

"Active8" <reply2group@ndbbm.net> wrote in message
news:h14ky9fam329.dlg@news.individual.net...

On 28 Apr 2004 10:37:50 -0700, majid wrote:

I am designing an electronic throttle control system for a go cart
and was wondering if anyone could help. I am planning on using a
stepper motor to move the throttle body, is that safe?(i heard it
would be better to use a servo but dont have one available) In the
event of the throttle being stuck open i was thinking of having a fuel
cut off solenoid to stop the fuel flow, is this a good solution, any
other ideas? I also need to take into account a whole lot of other
safety considerations such as what to do in the event of pedal
position sensor failure etc. any suggestions.

Another good safety mechanism is a key that attaches to your wrist.
If you wreck and are injured or freaking out, the key is likely to
pull out which would allow two contacts to make, shorting the
magneto to the block.
--
Best Regards,
Mike

The deadman switch should be on a lanyard, yes, BUT: plugging it
in should _enable_ everything. No plug, No Go. A shorting contact
to short out the magneto as well is also a good idea. Nothing wrong
with redundancy where safety is concerned.

And do not use a stepper. I've seen a stepper in a (conceptually)
similar application, and it (the whole project) was crap. Watson,
you might have seen the talking lion at the robot exhibit at the
OC fair, 10, maybe 15 years ago. That idiot used a stepper, with
a spring return, and we (I worked for him for awhile - have long
since lost track of him) had no end of problems with it.

RC servos will work, but you have to generate the PWM - this wouldn't
be hard, with a foot pot and a 555 or so, but another problem with
RC servos is that if they lose the signal, they freeze. This is NOT
what you want. So you need another failsafe, which cuts off the
throttle if the control goes either open _or_ short. You certainly
don't want it going full-throttle if you lose ground at your foot pot.

I'd probably go for an ordinary analog servo, with a spring return.

Good Luck!
Rich

 

[Tim Fish]

I feel obliged to ask why (I suspect for R/C control, but it would
be better if you tell). Mechanical throttle linkages have worked well
for many years.

Until now that is. I have already seen two newer vehicles that dont have
cables and are drive by wire. (in europe) The new renault clio sport cars
are throttle by wire. no cable at all (well apart from electrical cable
-) ) The same is true of the new BMW minis. If the software is properly
tested it can be much safer than cable throttle because it s harder for it
to jam open.

What is wrong with this group is that people question why somebody wants to
do something rather than just tell them how to do it.

well majid here is a straight answer... You can either use the throttle
adjusters from a new vehicle (expensive?) or use an RC servo. The drive by
wire throttles i have heard sound just like RC servos (the wine they make
when they move). You should add a spring to it though so that at loss of
power the throttle closes quickly (this is because RC servos stay where they
were when the power goes off). In any cart/car you should have a means to
cut the power anyway (all race cars here in the UK have to, to be allowed to
race)Cutting the power should cut the sparks and in turn cu the engine.

anything else just ask,
Tim

 

[Dave Cole]

in article Waamc.426$NK4.14645@stones.force9.net, Tim Fish at
timfishy@orange.net wrote on 5/5/04 13:15:

I feel obliged to ask why (I suspect for R/C control, but it would
be better if you tell). Mechanical throttle linkages have worked well
for many years.

Until now that is. I have already seen two newer vehicles that dont have
cables and are drive by wire. (in europe) The new renault clio sport cars
are throttle by wire. no cable at all (well apart from electrical cable
-) ) The same is true of the new BMW minis. If the software is properly
tested it can be much safer than cable throttle because it s harder for it
to jam open.

What is wrong with this group is that people question why somebody wants to
do something rather than just tell them how to do it.

well majid here is a straight answer... You can either use the throttle
adjusters from a new vehicle (expensive?) or use an RC servo. The drive by
wire throttles i have heard sound just like RC servos (the wine they make
when they move). You should add a spring to it though so that at loss of
power the throttle closes quickly (this is because RC servos stay where they
were when the power goes off). In any cart/car you should have a means to
cut the power anyway (all race cars here in the UK have to, to be allowed to
race)Cutting the power should cut the sparks and in turn cu the engine.

anything else just ask,
Tim


In the modern automotive cases I've seen, there are three separate pots

used in the foot feed and two or three feedback pots used in the
spring-return D.C. motor driven throttle actuator. Each pot has a specific
taper, polarity, and reference/ground potential such that any off-spec
signals cause an immediate shutdown (including fuel and spark delivery)
Redundancy is your friend when life-safety is in play.
Dave Cole