Unpowered sensor drives fibre optic cable??? - Page 1
Forum section: electronics / projects

author: Circlotron
author_rank: Super Contributor
timestamp: March 16, 2021, 02:32:10 am
content: This spark plug wire pulse sensor drives a fibre optic cable and the sensor itself appears to be unpowered because the only thing connected to it is the fibre. How can this possibly work?https://www.holley.com/products/ignition/ignition_boxes/power_grid_modules_and_accessories/parts/7555

author: richnormand
author_rank: Unknown
timestamp: March 16, 2021, 02:55:10 am
content: My guess:1)a neon bulb that lights up at the HV pulse field and sends light down the fiber. Most likely good only for timing purposes.2)There are companies making remote sensors that are powered by an IR beam of light down the fiber. A photodetector makes the dc needed for the sensor circuit.It then sends the data at a shorter wavelength back the fiber. Some fiber setups can handle a fair amount of power.

author: amyk
author_rank: Super Contributor
timestamp: March 16, 2021, 02:56:00 am
content: Inductor driving an LED.

author: floobydust
author_rank: Super Contributor
timestamp: March 16, 2021, 02:56:22 am
content: I would say it's using a current-transformer and (Schottky) bridge rectifier to drive the LED transmitter.Assuming spark current is a few hundred mA, and 20-50mA for the LED, you can guess the turns ratio. You can see the coil form bulge.The transmitter looks like something by Industrial Fiber Optics like IFE9x family.I've never thought Holley or MSD were particularly high tech for MCU implementations, to use this?

author: richnormand
author_rank: Unknown
timestamp: March 16, 2021, 03:22:36 am
content: You are right. Here is the instructions on the website:"Parts Included:1 – Inductive Sync Pickup1 – 12-feet of Fiber Optic Cable with Sleeve"Inductive coil driving an LED looks like.Bet you an old neon bulb (like the old Snap On test screwdriver to test ignition HV by putting the blade near the cable and look for the flash in the handle) coupled to the fiber might even be more rugged!

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 16, 2021, 04:23:09 am
content: Seems a bit overengineered when it would be trivial to pick up a signal from just that one wire using a coax cable with a little shielding on the end removed and then encased in plastic to clip onto the wire.

author: Circlotron
author_rank: Super Contributor
timestamp: March 16, 2021, 04:34:10 am
content: Quote from: NiHaoMike on March 16, 2021, 04:23:09 amThat would certainly work up to a point but the voltage signal on a spark plug wire is pretty noisy with a fair bit of ringing, so false triggering might be an issue. The current signal is much cleaner.

author: Terry Bites
author_rank: Super Contributor
timestamp: March 16, 2021, 02:27:06 pm
content: I agree with flooby. It looks like a current transformer with a LED and maybe some luxury diodes.If its cheap, why not!

author: mjs
author_rank: Regular Contributor
timestamp: March 16, 2021, 03:41:18 pm
content: Fiber port looked familiar, might be this one:https://i-fiberoptics.com/pdf/ife97-2-20.pdf, I've it in a high voltage isolated data link.