Car in a box - Page 1
Forum section: electronics / projects

author: mintynet
author_rank: Newbie
timestamp: January 20, 2019, 10:49:13 am
content: HiI'm currently building a 'Car in a box'https://www.mintynet.com/?page=hackfor use at security events to safely show others how to hack cars.I am using Ardustim on an Arduino nano to simulate the Crank and 2 Cam sensors and this works well. I am using a basic 555 circuit to simulate the two O2 sensors.The problem I am having is with simulating the ABS Wheel Speed Sensors, I have managed to use a basic DSO138 scope to get the following waveform for one of the sensorsThe waveform was created using the sensor next to a magnet rotating in a drill and the 10hz equates to approx 1mph.I have tried to use a XR2206 signal generator with either sine or triangle waveform but it does not seem to register any speed. The square wave output doesn't allow to vary the amplitude so cannot check thatCan anyone recommend a circuit that could possibly generate the correct waveform.Thanks in advancedIan

author: mjkuwp
author_rank: Unknown
timestamp: January 20, 2019, 11:48:17 am
content: I assume there may be multiple kinds of wheel speed sensors for ABS. The ones that I have seen do not use magnets and are called variable reluctance sensors. I think the signal is close to a sine wave. It will be low amplitude at low speed and increase from there.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 20, 2019, 01:31:38 pm
content: a simple 555 oscillator could do ? with some added transistors you could do up to 12v signal levels ??

author: mintynet
author_rank: Newbie
timestamp: January 20, 2019, 02:09:22 pm
content: I have tried the two circuits shown onhttps://forum.allaboutcircuits.com/threads/abs-speed-sensor-simulator.133901/and these do not seem to work. I may try them again but reverse the polarity.ThanksIan

author: max_torque
author_rank: Super Contributor
timestamp: January 20, 2019, 03:13:44 pm
content: There are broadly two types of wheel speed sensor:1) Old "voltage output" types, that are just VR sensors, that output a sine wave that is an amplitude and frequency proportional to the speed the target teeth are passing the sensorand2) Modern "current output" types that output a constant current (7mA no target and 14mA with a target in view). These can also have complex waveforms / edges that encode direction as well as speed

author: coromonadalix
author_rank: Super Contributor
timestamp: January 20, 2019, 03:41:34 pm
content: Maybe it need an zero crossing signal ? plus and minus voltage with an zero reference ?

author: james_s
author_rank: Super Contributor
timestamp: January 20, 2019, 07:20:30 pm
content: That may be the case. The ABS sensors I've seen are all VR types, they work like the pickup on an electric guitar and sense the steel teeth passing by.

author: mintynet
author_rank: Newbie
timestamp: January 21, 2019, 11:08:54 am
content: I have one of the ABS rings for the sensor and it is definitely magnetic, I'm going to try to build a rig to spin this next to the fixed sensors and see what I get on the scope.This could be used going forward but I would prefer an electronic circuit to generate the wave form as this would be smaller and require no moving parts.ThanksIan

author: Rerouter
author_rank: Super Contributor
timestamp: January 21, 2019, 12:12:18 pm
content: That exact waveform is from a proximity sensor that is fed through a AC coupling capacitor, with a biasing resistor tugging it back to ground, easy enough to simulate with your arduino aswell, just need to fiddle with the capacitor and resistor value to match what is on screen.Code:http://www.falstad.com/circuit/circuitjs.html?cct=$+1+0.000005+10.20027730826997+50+5+43%0AR+176+176+96+176+0+2+40+5+0+0+0.5%0Ac+176+176+256+176+0+0.00001+-2.12110699839023%0Ar+256+176+256+240+0+1000%0Ag+256+240+256+256+0%0AO+256+176+336+176+0%0Ao+4+64+0+4098+10+0.1+0+1%0A

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: January 21, 2019, 01:30:39 pm
content: Yep, a square wave ac coupled should do the trick.