Looking for a 12v source only when the car is in motion.
Registered User
Joined: Oct 2000
Posts: 7,134
Likes: 3
From: Columbia, MD
In layman's terms, what modifry was saying is a signal exists that changes its frequency in a very linear fashion compared to your speed. The signal swings from 0V to 5V and back again, probably at a very low current. One possibility, although I wouldn't say it's anywhere near a favorite, is to place a small capacitor across the relay coil to smooth out the signal enough to make it usable. The problem is, now you've got a small working voltage (around 2.5V average which may be too low for a cheap relay), and you're probably going to mess up the signal going to the tach without some sort of buffering.
It looks like both modifry and myself feel a quick/cheap circuit could be made with just a few parts to do what you're asking, but if the info he gave us makes no sense to you, designing and building one is going to be pretty difficult.
It looks like both modifry and myself feel a quick/cheap circuit could be made with just a few parts to do what you're asking, but if the info he gave us makes no sense to you, designing and building one is going to be pretty difficult.
Honorary Member
Joined: May 2001
Posts: 2,121
Likes: 3
From: Indian Land SC
[QUOTE]Originally posted by jeffbrig
[B]
Are you suggesting that if I generate the right waveform, I can fake the speedo into thinking I always drive 5mph and my odometer will rack up miles slower?
[B]
Are you suggesting that if I generate the right waveform, I can fake the speedo into thinking I always drive 5mph and my odometer will rack up miles slower?
Registered User
Joined: Oct 2000
Posts: 7,134
Likes: 3
From: Columbia, MD
Kenny, all kidding aside, your suggestion actually has merit...except for the fact that you can still be moving when you take your foot off of the pedal.
modifry, I can build that circuit in... (akin to Name That Tune
)
jeff, actually, I'm more of a software/firmware type of guy (DSP firmware, to be exact). MY MS taught me the hardcore theory, and the BS gave me the chance to really play with hardware, and some of that has always stuck with me. I love to tinker
Off the top of my head, you could use a transistor as a buffer. Use a cap as a connection to a second stage to allow only AC through (prevents the issue mentioned about the waveform stopping on a 5V peak). The second stage has enough gain to run a relay through a small rectifier network. Fairly simple and should do the trick.
modifry, I can build that circuit in... (akin to Name That Tune
)jeff, actually, I'm more of a software/firmware type of guy (DSP firmware, to be exact). MY MS taught me the hardcore theory, and the BS gave me the chance to really play with hardware, and some of that has always stuck with me. I love to tinker
Off the top of my head, you could use a transistor as a buffer. Use a cap as a connection to a second stage to allow only AC through (prevents the issue mentioned about the waveform stopping on a 5V peak). The second stage has enough gain to run a relay through a small rectifier network. Fairly simple and should do the trick.
Registered User
Joined: Oct 2002
Posts: 186
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From: Cortlandt Manor, New York
I WASN'T KIDDING!
ok, i was.
how about some sort of motion detector switch, maybe i/r with a relay?
or like a mercury or pendulum switch with a time delay?
the s2k does not ride that smooth.
ok, i was.
how about some sort of motion detector switch, maybe i/r with a relay?
or like a mercury or pendulum switch with a time delay?
the s2k does not ride that smooth.