Glove Controller

   Finished and mounted the homemade controller for my 'lectric gloves this
morning , photos of the installed item a
alt.binaries.pictures.motorcycles.harley if y'all wanna se what it looks
like .
  Haven't had a chance to rode test it yet , but sittin' in the yard it'll
turn 'em down to barely warm and crank'em up to Too Damn Hot . Works for me
!
I may have posted the p/n's here before , but in case I didn't , they're
from www.qkits.com , p/nMX033 and FB04 .

--
Snag
Learning keeps
you young !

 
I looked at the kits.

As a double-degreed electrical engineer who refuses to fix his own vehicle
electrical stuff beyond burned out light bulbs, I will give you one caution
...

The frequency spec'd is 100 Hz.  If you switch a heavy load in and out
repeatedly (which is what PWM'ing may do), you inject noise onto the
electrical bus of your motorcycle.  There is a very small possibility that
you could create problems with electronics on the motorcycle or the charging
system.

Automotive electrical modules have to be designed for extreme noise due to
things of an inductive character that are powered.  A typical automotive
module has to be able to take 60V for a very short period of time, and
reject other frequencies that appear on the electrical bus.

Motorcycle components may or may not be designed to the same standards.

The probability of problems would increase if you were controlling an
inductive load (which I think you are not), and the probabilities would
increase if the gloves draw a large amount of current (which they probably
do not).

Without an inductive load, I would not expect damage to any components on
the motorcycle (just possible anomalous operation).

So, if anything unusual happens, we could discuss strategies to even out the
current draw ...

DF

 Datesfat Chicks wrote:

  snipped the cautions ...


  I've fused the circuit at 3 amps , which is about 35% over the rated draw
of the gloves . As far as I know , the controllers sold by the glove mfrs
are also PWM's , and they're also rated for jackets/liners and pants . I
don't foresee any problems , but do appreciate the heads-up . Would one of
those strategies involve a rather large capacitor ?
--
Snag
Learning keeps
you young !

 
Generally, what you'd try to do is eliminate the high frequencies in the
current draw from the cycle's electrical system, i.e. make the current draw
look as much like a constant non-PWM'd load as you can.

One possibility is to operate a transistor in its linear range (rather than
in cutoff or saturation).  However, this will create heat dissipation issues
in the electronics and is wasteful.  PWM'ing is the more efficient approach.

A large capacitor alone on the input to the electronics won't be quite
enough.  There are a couple of issues:

a)When you first connect the controller, there will be a large current draw
as you charge the capacitor.

b)The capacitor won't be wholly effective.  You probably would want to add a
modest power resistor before the capacitor, which addresses (a) and also
evens out the current flow in PWM operation.

What would effectively happen is that when the PWM turns on, it draws its
current from the capacitor, and the power resistor prevents the change in
voltage on the capacitor from resulting in too much current flow from the
motorcycle's electrical system.

A capacitor alone might be effective in practice because the resistance of
the wiring leading to the controller would do the same job as the power
resistor mentioned above.

So, yeah, a huge-ass capacitor is in the right direction.

Also, 100 Hz is kind of low frequency.  The higher the frequency, the
smaller the capacitor can be.  But also it means you keep the FET in the
linear region for longer, which will cause more heat dissipation in the FET.

DF

   On 11/21/2010 5:11 PM, Datesfat Chicks wrote:

As was already mentioned several times, it is very unlikely that the PWM
controller described here is going to cause any problems whatsoever with
the bike's electricals.  In the unlikely event that it does interfere
with something
that is especially sensitive, there are some simple filtering, etc.,
fixes that
should be applied long before you get into recommending a linear regulator,
etc., to "solve the problem."


Which, as long as the inrush current isn't excessive, won't be a
problem.  If
this inrush IS a problem, there are better ways to deal with it than by
throwing
away power (and losing input voltage) via an inline power resistor.  An
inline
choke or an inrush-limiting thermistor would be preferred.


A choke would do a better job of "evening out" the current flow without
wasting the power or dropping the DC input voltage.  Biggest drawback
to a choke is generally size and/or weight, but neither may be an issue
here.

The problem with such loads may not be at the frequency of the PWM
action itself, but rather the higher-frequency noise resulting from the fast
switching transients.  To deal with these, a smaller capacitor should
generally
be paralleled with any "big-ass" filter cap, as the large caps are typically
ineffective at filtering RF.

Best advice to start with, though, is just to give the controller its
own power
line, run as directly as possible to the battery terminal and using as heavy
a conductor as is practical.  Keep that run short, direct, and away from
those lines supplying other loads, esp. those which may be sensitive to
switching transients.  The battery itself is generally a pretty effective
"noise filter."  You may still need the other components if noise issues
crop
up, but that's always the first step to take.

Bob M.