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Hi friends,
first of all, excuse-me for my Biiig delay in posting this message.
I was on vacation and far away from computers ! It was hot and sunny and very peacfull and there were girls and drink and all the other things.
Well, IÂ'm doing my speedometer using a processor.
The Timer 0 counts a 250 MS period and Timer 1 works as a pulse counter.
I know that my Opel Corsa has a Speed Sensor (VSS) which could be used to give me the right number of pulses for each carÂ's wheel revolutin (i guess it is 8 pulses / revolution in a 14 inch wheel)
IÂ'm trying to do a Schmitt Trigger with a Ne555 to capture de pulses from a sensor
The problem is that in this bad country no one wants to give the right information about the sensor. Everybody wants to sell the information in book for about US$ 80,00 ! ! ! ! ! !
have you ever did something with carÂ's Speed sensor ? Is the output of this kind of sensor in low voltage enough to work with the 555 ?
If you have any information about the speedometerÂ's implementation... Anything.... Iwould be happy !
thank you !
Sérgio
this is a two wire device and as such a comparator should be employed.
The 555 is overkill and the fact that the comparator in the referenced schematic does not have positive feedback (schmitt) is even more stupid. Having the comparator drive a capacitive load (C2) defies the rule every article/book re op-amps states.
Erik
Erik Mallard,
i ask profesional and he say that the one i saw was very good and reliable and not stupid.
If you think you do better circit you must give it for me to try.
Why do you single-out Erik?
Note that Per has aslo said, "I don't like the linked schematics"
There is really no point in discussing schematics until you've confirmed that this is the sensor that is actually fitted in your car!
Or, at least, that it's the same type of sensor.
Have you done that yet?
Of course, this is not the right forum for discuccing schematics at all - it has nothing whatsoever to do with Keil software tools, does it?!
"There is really no point in discussing schematics until you've confirmed that this is the sensor that is actually fitted in your car!"
For instance, see takes its reading from the position of the speedo needle" (my emphasis)
If your car is the same, then it will require an entirely different approach from the link you posted!
If you think you do better circit you must give it for me to try. Again if we ASS U ME that the Corsa has a sensor like the one the bascom link refer to the first thing is do nothing that interfer with the ECU (Engine Control Unit). If you attach the bascom circuit your car will probably malfunction because the ECU does not pick up the speed info (probably the Bascom circuit will not work either). so much for "i ask profesional and he say that the one i saw was very good" That, of course, could be because you witheld vital information from him.
Thus you have to pick up the signal from whatever the ECU employs and NOT the 100 ohm resistor the Bascom thingy uses. So, jack up the Corsa attch a scope and rotate whatever wheel drives the speedometer. You should see some pulses, till risietime falltime and voltage of those is known there is no way I can "give it to you to try".
PS I get the impression that the "bascom" circuit the OP keep referring to is not of Bascom origin, but posted at the Bascom site by someone.
The speed sensor is located in the speedometer and takes its reading from the position of the speedo needle I doubt it, simply because that would be quite difficult to implement if, indeed, the "speedo needle" is a needle. Much more likely would be pulses from whatever rotates in the speedometer.
Anyhow, all that has been posted so far, from anyone, ASS U ME that the input to your unit will be pulses.
that needs to be verified as well as the things mentioned in my former post.
Sorry for long delay in respond but I talk to John and Mantra.
We talk to my profesional friend again and he say he has good working circut for my car and say i can ignor your ASS U ME and dangerous silly bad sugestions. it connetcs to the ECU thru plug and switches safeblock.
Mantra has started on the code soe we try soon.
1) I have no idea who Erik Mallard is 2) How can no suggested method till you measure the pulses be a dangerous silly bad sugestions 3) You go ahead and blow the ECUs sense of the speed, I am not a carbuff and have no idea what that will do to the ECU, it is up to you whether to take the risk. 4) If you parallel the 100 ohms with whatever the ECU uses for sense you WILL upset something. and, if the ECU uses high side sense you will blow it. 5) Who is "John and Mantra", not that I care, just do not bring up things in a forum nobaody can decipher. 6) I wonder why you refuse to measure the pulses going into the ECU. That would establish a firm base for the design. 7) If you live where Christmas is celebrated, have a merry one.
Erik,
Sorry I got your wrong name.
Wish you (and all others peoples that naswered) a Merry Christmas too.
buy for now.
"that would be quite difficult to implement if, indeed, the "speedo needle" is a needle"
I agree it does sound a bit odd - but not entirely improbable...
It depends on what "speed" info the ECU actually needs - if it's just a crude stop/slow/fast, this might be fine... (remembering that a Corsa is a low-end car)
It might have a slotted opto thingy to detect the needle movement. If this is a fairly early car, before they went all digital, that would've been a cheaper development than a complete electronic speedo from scratch...
But the point is: the OP needs to know what it is before even thinking about what circuits may be "good" or "bad" for handling it!