VSS signal simulator?
Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=65711
Printed Date: July 17, 2025 at 12:27 PM
Topic: VSS signal simulator?
Posted By: mmh1
Subject: VSS signal simulator?
Date Posted: November 06, 2005 at 2:18 PM
Hi,
My alarm has a VSS signal input to lock the central locking when the car is on the move. By utilising the vehicle speed sensor (VSS) from the speedo.
The input requires a pulsed negative input.
My problem is the alarm is fitted to a classic car, a MINI to be exact from the days of totally mechanical instruments so no VSS available!
Can anyone help with a way to simulate the signal for input to my alarm system?
Many thanks, Mo
Replies:
Posted By: x77911
Date Posted: November 06, 2005 at 9:00 PM
several companies that offer GPS/navi systems offer speed pulse generators that can be fitted to cars like yours example: https://www.sjgreatdeals.com/avx2504165.html ggod luck
Posted By: tragik
Date Posted: November 06, 2005 at 10:45 PM
You can do it the old school (cheap) way. Take a magnet and secure it to your driveshaft. Then, nount a all weather magswitch in close proximity to magnet as it rotates with the driveshaft. If done right, the switch will close with every rotation of the driveshaft, and give you the pulsed output you are looking for. They make kits for this, but they are essentially the same thing, and cost more money.
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Northstart.....or start it your damn self.
Posted By: mmh1
Date Posted: November 08, 2005 at 1:48 PM
Sounds good to me.
But I just wanted to see if there was some sort of circuit to produce a simulated negative pulse.
Unfortunately in the UK we can't get DEI pulse timers and PAC TR7 programmable relays...so very limited.
As for extra sensors etc. that seems very expensive to me.
Thanks. M
Posted By: tragik
Date Posted: November 08, 2005 at 10:05 PM
the mag sensor i was talking about only costs 3 dollars. U.S. Dollars that is. I don't know what the exchange rate would be, but its still cheap.
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Northstart.....or start it your damn self.
Posted By: mmh1
Date Posted: November 09, 2005 at 2:35 AM
Thanks tragik,
I'll have a look in Maplin's (the equivalent to your US Radioshack).
Just wondering, what if I am stuck in traffic would the alarm just unlock when not moving? I'm not too sure.
Someone suggested to me attaching it to the negative terminal on the ignition coil so it locks while the car is running, any thoughts on that????????
M.
Posted By: tragik
Date Posted: November 10, 2005 at 1:27 PM
I dont think it will unlock when you stop. In fact, using a magnet/switch set up will behave exactly like your cars vss system. Typically, speed dependant locking systems will unlock when the ignition is turned off. I wouldn't tag this wire to the coil. The coil's output is a pulsing negative output, but I am not sure if the voltage is to great for the input on your device. ------------- Northstart.....or start it your damn self.
Posted By: mmh1
Date Posted: November 10, 2005 at 1:36 PM
Thanks tragik,
I think I'll stick to your magnetic switch idea, sounds do-able to me 
Did you mean the pulsing negative output from the coil will be a too higher voltage or it won't be high enough????
Thanks, Mo
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