Ivar Rand on sun 9 mar 97
I am making this enquiry on behalf of a potter friend who has the
following problem:
At present he has a crackling sound when listening to the radio and
throwing on his new Shrimpo Master Serious wheel. Shrimpo has indicated
nothing can be done about it. I wonder if anyone has experienced any radio
interference when throwing on the new master series wheel.
Ivar Rand email: ivar@freenet.edmonton.ab.ca
4627-107 Ave. Phone: 403-466-6138
Edmonton, AB, T6A 1L8
Gavin Stairs on mon 10 mar 97
>...a crackling sound when listening to the radio and
>throwing on his new Shrimpo Master Serious wheel...
Hi Ivar,
This sounds like switching harmonics from the electronic motor control on
the new Shimpo wheels. This could also be a problem with other electronic
speed control wheels. It arises from switching the motor current on and off
very quickly in order to control the wheel speed. It is the same sort of
interference you get on am radio from your car's ignition.
Shimpo probably says there's nothing they can do because it is a question of
circuit design. Nevertheless, it may not be exactly true. More likely a
question of economics. There are several ways to slow down the switching
transient, which would have the effect of reducing or eliminating this radio
interference. Unfortunately, they all cost some money. If your friend
wants to try, he can attempt to kill the noise by attaching a capacitor
across the motor terminals, but without having the Shimpo circuit diagram in
front of me, I can't advise on this.
If this is of concern to you, take along a transistor radio when you go to
purchase a wheel, and tune it over the am band while you sit at the running
wheel, listening for a whine that goes away when you turn the wheel off.
RFI is subject to regulation. I wonder if the Shimpo wheel is entirely
legal in this respect.
Gavin
John Post on mon 10 mar 97
I had the same problem with radio interference when I was throwing on my
Shimpo Masters Series wheel. I tried putting a surge suppresor and
grounding plug into the wall socket and then hooking the wheel and radio up
to that. It didn't fix the interference. I solved my problem by running my
wheel and radio on different electrical circuits. Each circuit is
controlled by a different breaker in the box.
I hope this helps,
John Post
At 11:06 AM 3/9/97 EST, you wrote:
>----------------------------Original message----------------------------
>I am making this enquiry on behalf of a potter friend who has the
>following problem:
>
>At present he has a crackling sound when listening to the radio and
>throwing on his new Shrimpo Master Serious wheel. Shrimpo has indicated
>nothing can be done about it. I wonder if anyone has experienced any radio
>interference when throwing on the new master series wheel.
>
>
>Ivar Rand email: ivar@freenet.edmonton.ab.ca
>4627-107 Ave. Phone: 403-466-6138
>Edmonton, AB, T6A 1L8
>
Bill Aycock on tue 11 mar 97
At 09:48 AM 3/10/97 EST, you wrote:*** in snipped parts ***
>----------------------------Original message----------------------------
>>...a crackling sound when listening to the radio and
>>throwing on his new Shrimpo Master Serious wheel...
>
>
>This sounds like switching harmonics from the electronic motor control on
>the new Shimpo wheels.
>Shimpo probably says there's nothing they can do because it is a question
of circuit design. Nevertheless, it may not be exactly true.
>
>
>>RFI is subject to regulation. I wonder if the Shimpo wheel is entirely
>legal in this respect.
>
>Gavin
>
Gavin et al--
First- when they say "there is nothing we can do about it"-- simply put-
WRONG. shielding and clip-on filter chokes (available at Radio Shack) will
fix the problem.
Second- the problem is poor design. The treadmill Iris uses, the CI wheel I
use, and lots of other gadgets use similar controls- with no problems.
Third- The RFI is subject to regulation, and the level reported is in
violation of regulation. Unfortunately, the regulations are not being
enforced because of the downsizing of the FCC and other protective agencies,
like the Weather service, in the current flury of cutting back to "REDUCE
GOVERNMENT INTERFERENCE!" The good guys get their throats cut first.
However, Shimpo may not know this, and a threat to report their violation of
interference regulations to the FCC may make them do something.
Seriously- try getting a clip-on filter choke (it is a short hollow cylinder
of powder-metalurgical stuff) from RS, put it on the wire leading from the
control unit to the pedal. Another, on the power wire, near the wheel, might
help. These wires act as transmitting antennas, and the choke does just what
its name says- it chokes circulating RF currents. Many computers have one
molded into the cable from the monitor to the CPU. (It is a cylindrical lump
in the wire).
Bill- on Persimmon Hill, where the worst RFI is TO my Ham radio from my
computer !
Bill Aycock --- Persimmon Hill --- Woodville, Alabama, USA
--- (in the N.E. corner of the State)
also-- W4BSG -- Grid EM64vr baycock@hiwaay.net
Gavin Stairs on fri 14 mar 97
Peter Freihofner wrote (to me, apparently instead of to the list):
>Someone suggested putting a capacitor across the motor terminals...
>
>D O N O T D O T H A T !!!
>
>Depending on the quality of the protection circuitry for the switching
>devices, the result of bypassing the switched inductive load (anchor coil
>of the DC motor) could be anything from reduced drive capability to a
>destroyed speed regulator board.
>
>I strongly suggest getting back to the wheel manufacturer with your query
>and he will be able to make recommendations.
>
>Hope this message is getting to the right address in time.
Also, Frank Tucker wrote to the list concerning Shimpo's response.
If you don't understand what you are doing, don't do it: wait for the right
answer from Shimpo, or someone who has worked it out first hand. My comment
re: capacitor was made in that light. If the speed control has the right
kind of commutation, the capacitor trick will work. Otherwise an inductive
trick (e.g., the clip-on filter choke suggested by Bill Aycock) may work.
The REAL solution is to redesign the controller so it doesn't make hash in
the first place. Caveat hacker.
Gavin
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