Bicycle Mechanics - Speedo and light not working together?!

This is an odd one. I recently installed a Planet Bike Blaze 1W light on my handlebar next to my Trek Incite 8i wireless speedo. They are about 4 inches apart. When I turn on the light the speedo jumps up +/-40mph until I turn off the light. I'm guessing they're working on similar frequencies or something like that but am wondering if there's anything anyone else has tried to solve this beyond switching out the light or the speedo? Also, if I switch out the light are there others I should avoid so I don't duplicate the problem?

Interference. Nothing you can do about it. You can try placing the light further away from your computer but I doubt you can get it far enough to matter.

the PWM (pulse width modulation), a form of voltage restriction, in the light is the main cause.

wired computer or run your light at full power with no strobe.

I had the same problem with a Planet Bike Blaze light next to a Sigma wireless computer. At first I thought it was because it was at night and therefore colder and the computer battery was not as effective. When I switched to a Sigma light the problem went away.

the PWM (pulse width modulation), a form of voltage restriction, in the light is the main cause.

wired computer or run your light at full power with no strobe.
I wonder if even running at full power will solve the problem. Many lights use PWM even at full power to keep voltage to the LED or bulb constant as battery voltage falls off during discharge.

I had the same problem with a Planet Bike Blaze light next to a Sigma wireless computer. At first I thought it was because it was at night and therefore colder and the computer battery was not as effective. When I switched to a Sigma light the problem went away.

I have the same problem - thanks for the heads up on switching to Sigma brand. What light did you choose?

I wonder if even running at full power will solve the problem. Many lights use PWM even at full power to keep voltage to the LED or bulb constant as battery voltage falls off during discharge.

Correct, it probably won't help in this case. The Blaze is LED based and they use a switching (PWM) supply to create a constant and regulated current supply to drive the LED.

I wonder if even running at full power will solve the problem. Many lights use PWM even at full power to keep voltage to the LED or bulb constant as battery voltage falls off during discharge.

I'd have to say it depends on the model.
some only use PWM when strobing
some only use PWM when in low or mid
some use PWM consistently through all modes.
some have really good shielding so the PWM doesn't interfere with other wireless devices.

I had this problem with my light/wireless computer. I went back to a wired computer because of it.

Apparently HID lights are the worst for interfering with wireless computers. I run a wired computer on my commuter for this reason. I never had any issues using a wireless Polar computer with a variety of Cateye LED lights though.

Old thread comes alive...

I recently discovered this issue too - I have an el cheapo cycle wireless computer (from MEC in Vancouver) which doesn't like the PWM used on low and strobe modes of the Planet Bike BLaze 2 Watt light. Whatever my current speed is at time of activation of the light remains. When the Blaze 2W is set on high output, the problem disappears. I recognized this immediately as a sign of RFI between the light and the cycle computer (I'm a ham radio geek from years back).

I don't like PWM. It isn't necessary to get good run times out of high power LED lights, and proof exists in the Fenix line of high output LED flashlights. These (at least the models I buy) have current controlled regulation rather than pulse width modulation for output control. On my bike as a secondary light to the Blaze I use a Fenix LD10 R4 (1h 45m on 'high', not 'turbo' off a single AA rechargable cell) and in a recent technical review it came out as a runtime and output champion against a dozen other comparable lights. Even on high frequency strobe it causes no interference with the el-cheapo computer.

I suppose I could go wired but I'd rather find a not-too expensive wireless computer that isn't affected by the Blaze 2W on its strobe and low output setting. Anyone out there have such a combo that works?

Alternatively I can just get a second LD10 R4... and keep the el-cheapo computer which meets my minimal needs in that department.

Apparently HID lights are the worst for interfering with wireless computers. I run a wired computer on my commuter for this reason. I never had any issues using a wireless Polar computer with a variety of Cateye LED lights though.

+1 I had this with a Cateye Wireless 7 and Niterider MOAB HID headlight. Switched to an Astrale 8 wired, and no more problems. Picked up cadence too!:thumb: