Subject:
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Sensor questions
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Wed, 12 Jan 2000 15:16:26 GMT
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Original-From:
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Jonathan Swaby <JONATHAN.SWABY@VPSS.antispamGATECH.EDU>
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Viewed:
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610 times
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I have several sensor questions.
I would like to use my miniboard as an engine management system. At the present
time, I have a small 2 cycle engine from a weed wacker that I would like to
control. I would like to have the miniboard gather some information about the
atmospheric conditions and use that information to adjust the air fuel mixture.
I figured that I would start with what I thought would be the easiest, sensing
the temperature. I have played with a couple of devices (LM34, LM335, and a NTC
thermister). The thermister was the first device I found. It works well, but it
is not linear. Next I played with the LM335, with and without adjusting it. This
also works well, but I can't figure out how to convert the output from the
miniboard into a temperature. 1 C = 10Mv. I then tried the LM34. There is no
calibration pin and it uses farenheit. 1F=10Mv. For some reason, the output from
this device varies very little with changes in the room temperature. Now the
present room temperature is 58F, during the summer it was 78F. The miniboard
returned a value of 158 for both of these temperatures. If I use a voltmeter to
measure the voltage between ground and the signal pin it reads around 1V.
Strange. Ideally, I would like to use the LM34, but the LM335 seems to work much
better. That is it is more responsive. Does anyone have any tips on how to use
anyone of these devices with the Miniboard or the Handyboard? How to connect
them and how to calculate a temperature for the output? I am not wanting to
remove the pull-up resistor from the circuit, if that makes a difference. I am
also using ICC freeware to program the Miniboard and IC on the HandyBoard.
I would also like the board to sense air pressure and humidity. I have read
about capacitors that will vary with humidity, but I have no idea how to make
them work with the Miniboard. Can anyone provide any tips on this.
Lastly, I would like the miniboard to track the engine rpms. I have a few ideas
on how to do this, but I am not sure about any of them. I figured the easiest
way might be to use a reflectance sensor pointed at a nut on the crankshaft. I
would paint all but one side of the nut with black paint, and glue a piece of a
cd on the one unpainted side. Another idea is to use something on the spark plug
wire. I thought a hall effect sensor might work, but I am not sure. Along the
same line, I read an note in this months Nuts & Volts about using an inductor on
the spark plug wire and a chip to convert the output to a voltage. I am sure I
have over simplifed here. I don't remember all of the specifics. Assuming I use
one of the first two methods, how long do I need to sample to port to get a
reasonable number for the rpms? Does anyone have any suggestions on the method
that would be best to use?
Thanks
<bold><bigger>Jonathan Swaby
</bigger>Computer Services Specialist IV
Student Affairs
Phone: 404-894-5889
Fax: 404-894-9928
<color><param>0000,0000,8080</param><bigger><bigger>
Georgia</bigger></bigger></color></bold><bigger><bigger><italic><color><param>8080,8080,0000</param>Institute
of</color></italic><bold><color><param>0000,0000,8080</param>Tech</color></bold><italic><color><param>8080,8080,0000</param>nology
</color></italic></bigger></bigger>
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Message has 4 Replies:
 | | Re: Sensor questions
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| (...) SNIP (...) Newark electronics used to sell a humidity sensor based on this principle for about $ 12. It should still be available. I believe it was made by Phillips. Basically the variations in capacitor value is used to vary the frequency of (...) (25 years ago, 12-Jan-00, to lugnet.robotics.handyboard)
| | | Re: Sensor questions
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| (...) Sounds like fun! Go check out the EFI332 (hope I got that right) project. That's a project to build a 68332 board to control a larger engine. They'll probably have pointers to the different types of sensors that can be used with it, some of (...) (25 years ago, 12-Jan-00, to lugnet.robotics.handyboard)
| | | Re: Sensor questions
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| You wrote: I then tried the LM34. There is no calibration pin and it uses farenheit. 1F=10Mv. For some reason, the output from this device varies very little with changes in the room temperature. Now the present room temperature is 58F, during the (...) (25 years ago, 12-Jan-00, to lugnet.robotics.handyboard)
| | | Re: Sensor questions
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| (...) The Electronic Surplus Dealer Goldmine, (URL) been selling some weather balloon electronics innards for a few years. On this board there are some relevant sensors: a thermistor, some sort of barometric chip and a humidity "device". The (...) (25 years ago, 13-Jan-00, to lugnet.robotics.handyboard)
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