Smart Shock interference with wireless computer?

[Tom_A.]

Here's an interesting problem...I was wondering if anyone else had experienced this.

I have a Ciclosport CM414 Alti M computer that I've used with my road bike for a couple of months.  It's a wireless computer that has a memory and records elevation profiles from rides.  I decided I wanted a cadence mount for my road bike, so I bought one and finally put it on.

Of course, I then installed the wireless mount on my '99 4000.   I was really looking forward to getting elevation plots of some of my local rides...but I ran into a problem.

If I turn on the Smartshock mounted to my crosslink, the speed readings of the computer goes to zero.  I turn it off, and the speed reading is normal.  Obviously, the Smartshock is generating electromagnetic interference and blocking the signal from the wheel sensor mounted on the fork leg.

I'm going to try moving the computer and wheel sensor around and see if I can find mounting location where this doesn't happen.  If that doesn't work, I'll maybe even try to make a shield for the Smartshock.

Anyone else ever have this problem?  Any suggestions?

[kiwi]

I used too be a draughtsman for NZ's telephone network company(at that time govt owned and the ONLY telephone company.We used to clad the entire building in .55 mm stell sheet before any "proper cladding went on..to protect the exchange from radio interference.I am not sure if the shell was "powered" or not.

[Old Proflexer]

i took the computer off my mountain bike a ways back

it was disappointing to see how fast or how far i was actually going (compared to my old road days)

in the end i just decided i was going for a ride, it didn't matter how far or how fast, i was just going to enjoy the ride and company and push things at my own limit, whatever that may be for that day -

i'd reconsider a bar mounted heart rate monitor tho
but i'd hate to see that go to zero right before my eyes -
that would not be good

OP

[jimbo]

I use to have a Corvette that had a shielding over the Distributor to prevent interference with the radio.  The Corvette had a fiberglass body and firewall which is why the distributor interfered with the radio without the shielding.  I seem to recall the shielding was a plastic cover lined with a tin foil type material.   You might wrap tin foil over the electronic part of the shock.  Of course, don't blame me if the electronics mysteriously self-destructs.

[Dennis]

all you need to do is put what's called a "Faraday cage" around the smartshock. Jimbo's idea of tin foil should work fine. even a wire mesh (like a window or door screen) would work.
its the same principle as to why you are safe inside a car during a lightning storm (and no, it has nothing to do with the rubber tires acting as insulation, if the car gets hit the current goes right through the tires into the ground).
let us know how it works out.
[smiley=groucho.gif]

[Scott]

Good thing none of us ride with a pacemaker....

[Carbon_Angus]

i'd reconsider a bar mounted heart rate monitor tho

but i'd hate to see that go to zero right before my eyes -

that would not be good



OP

yeah, but what a way to goooo!!! it's the second best way to go, i reckon [smiley=laughing.gif]



[smiley=beer.gif] [smiley=beer.gif]

[Tom_A.]

Pacemaker...ha, that's funny, that's exactly what a friend at work said after I told him about it.

...Here's the update.  I tried moving both the receiver and the sending unit around but couldn't find a location where the smartshock wasn't "jamming" the signal from the wheel sensor.  So...it was time to do a bit of "investigative engineering".  I pulled the smartshock off the fork and removed the 3 torx screws that hold the plastic bodied electronics assembly.  This allowed me to get a better look at the electronics.  I also peeled up the sticker in the base of the battery compartment and removed the screws installed there.  I then had a pretty good look at the whole scheme.

The majority of the electronics are mounted to a single printed ciruit board mounted directly behind the battery in the largest portion of the plastic body.  From the large portion, 2 flex circuits are routed through the "thin" portion of the plastic cover.  One flex connects to the piezo valve mounted in the aluminum shock body, and the other flex has a magnetostrictive sensor placed at the end.  This sensor resides in a small pocket in the shock body and acts as the proximity/velocity sensor based on the magnetic field it picks up from a magnet mounted to the end of the shock shaft.  Either one of these flexes would act as great antennas for EMI...I suspect it's the flex going to the piezo valve that is the culprit.

Anyway...after poking around, it was very obvious no considerations were given in the design to miminize RF emissions, so I resorted to the old troubleshooting standby of copper tape.  This is thin copper tape with an adhesive backing.  I covered virtually all of the plastic housing with the tape except for the battery cover and the switch panel.  I took care to make sure that a couple corners of the tape were sandwiched between the aluminum shock body and the plastic housing to get a good electrical connection and created a "faraday cage".

The result....everything works great now.  The only downside now is that part of the shock looks like it belongs on a satellite    Also, I'm sure the copper will corrode nicely...I would've used aluminum tape if I could have found some....I'll see if I can find some when it comes time to replace the shield.

[tmaybee]

Try muffler tape.  I think that is aluminum.  You can also buy aluminum ductape.

Trevor