Identify / hack this sensor... - Page 1
Forum section: electronics / general

author: int2str
author_rank: Regular Contributor
timestamp: July 11, 2016, 04:28:45 am
content: Attached is a sensor I pulled out of my car's windshield washer fluid reservoir.So this essentially detects whether I have fluid in that reservoir.The Inside what looks to be a sealed glass bulb are two "electrodes" that do not seem to be touching (capacitive?).Anybody want to venture a guess on how it works?I want to emulate it to keep the windshield washer light off on my dash (converting to race car)...

author: ataradov
author_rank: Super Contributor
timestamp: July 11, 2016, 04:46:35 am
content: It is a reed switch.

author: jh15
author_rank: Frequent Contributor
timestamp: July 11, 2016, 04:55:23 am
content: Like a weather rock, can't you just look at the tank to see if it is dry.Edit:oh race car, just tape a magnet on it.

author: vk6zgo
author_rank: Super Contributor
timestamp: July 11, 2016, 04:59:02 am
content: The glass thing looks in every respect like a reed relay.These are operated by a magnetic field,either from a permanent magnet or an electromagnet.How windshield wiper fluid changes a magnetic field,I do not know----are you sure the sensor is complete?If it still works,fill the reservoir & look at the input connections with a multimeter.First,check the resistance with the connection to the car electrical system unplugged,& record that,then with it normally connected,check what voltages w.r.t car chassis appear on each pin of the connector.Empty the container & do the same tests-------what changes?

author: ataradov
author_rank: Super Contributor
timestamp: July 11, 2016, 05:00:15 am
content: Quote from: vk6zgo on July 11, 2016, 04:59:02 amI'm pretty sure there is corresponding floating magnet somewhere there.

author: int2str
author_rank: Regular Contributor
timestamp: July 11, 2016, 05:04:29 am
content: Tested with a magnet, reed switch it is - that was easyThat means I can just short the wire and be done with it.Thanks guys!

author: Brumby
author_rank: Unknown
timestamp: July 11, 2016, 05:39:53 am
content: Quote from: ataradov on July 11, 2016, 05:00:15 am+1

author: tszaboo
author_rank: Super Contributor
timestamp: July 11, 2016, 08:57:02 am
content: Quote from: ataradov on July 11, 2016, 05:00:15 amNo, washer fluid is ferroelectric.

author: Kjelt
author_rank: Super Contributor
timestamp: July 11, 2016, 09:17:48 am
content: Quote from: int2str on July 11, 2016, 05:04:29 amOr the other way around keep it open, depending where the sensor is mounted and the corresponding floating magnet, if it is an empty indicator I would presume that the switch only makes contact when the level is low.

author: amyk
author_rank: Super Contributor
timestamp: July 11, 2016, 10:20:33 am
content: Quote from: int2str on July 11, 2016, 04:28:45 amWhy don't you just unplug/remove the light? Might even save some weight

author: rrinker
author_rank: Super Contributor
timestamp: July 11, 2016, 03:08:27 pm
content: That was what I was going to say after I read the first post.

author: int2str
author_rank: Regular Contributor
timestamp: July 11, 2016, 11:17:31 pm
content: Quote from: Kjelt on July 11, 2016, 09:17:48 amGiven that the sensor is on my bench and the light is still on in the car, imma gonna go with it is normally closed to turn the light off

author: vk6zgo
author_rank: Super Contributor
timestamp: July 12, 2016, 02:21:45 am
content: Quote from: ataradov on July 11, 2016, 05:00:15 amNice selective editing,AlexThe whole sentence was:-"How windshield wiper fluid changes a magnetic field,I do not know------are you sure the sensor is complete?"The last part implies that there must be some mechanism to move a magnet with water level,although it was not obvious from the pix.I didn't think I had to "spell it out" on this forum!Of course,you could heat the magnet above its Curie point,then cool it down with the water,but I very much doubted that would be the case!

author: jh15
author_rank: Frequent Contributor
timestamp: July 12, 2016, 04:17:19 am
content: Many years ago, somewhat after 9/11 attacks, we (my avionics firm people) were life testing an oil level detector for a Cessna or some airplane.The jig was running a magnet float over a reed switch.A response from one of the magnet or switch vendor's asked: Are you building a bomb?The test run of many months happened to terminate on 9/11 anniversary.Now I know NSA just perked its ears at me.