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46  Using Arduino / Project Guidance / Re: Vehicular emissions sensors ? on: September 23, 2014, 06:45:46 pm
All emissions equipment uses a sniffer and a pump to sample the exhaust.

Cool exhaust is sucked into the machine, i have never met an emissions station that reads Lambda {air fuel ratio}
All the ones used for MOT testing in the UK measure Lambda. They have to, by law.
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Lamda correlates to a cars performance, but not to its emissions, specifically.
If you know the NOX the lambda is irrelevant.
And vice versa. UK exhaust testers do not measure NOX, only CO, Hydrocarbons and Lambda.
47  Using Arduino / General Electronics / Re: Momentary dip switch? on: September 22, 2014, 11:36:56 pm
They could be 2 bays wide: 4 buttons in an dil-8 length, would be very handy.
Maybe some very small microswitches, like those used in a mouse, would work?
48  Using Arduino / General Electronics / Re: 12v input to 7805 voltage regulator heating in a second?? on: September 22, 2014, 11:12:26 pm
For a TO220 device something like 0.5W is the maximum you'd really want to
put into it without some sort of heatsinking.   If you have 12V supply to a 7805
that's suppling 70mA you will be at 0.5W dissipation already.

If you put 1.5A through it the dissipation will be 1.5 x 7 = 10.5W and a medium
sized heatsink and a fan would be required (or a large heatsink).

A DC-DC converter would waste much less power and run at a sensible temperature
without such issues....
Or you could use a L78S05 (rated at 2A max), but you'd still need a heat sink.
49  Using Arduino / Programming Questions / Re: Avoiding Delay (blinkwithoutdelay) help on: September 22, 2014, 11:04:54 pm
I may be wrong, but I seem to remember reading that the microseconds counter is only updated every 4 micros. How then, can there be a measured 5 microsecond delay?

Good point, he can't smiley-wink
Its probably going to return either 4 or 8 depending on the system overhead.
I can't see it returning 4 if he's asking for a 5 micros delay.
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I cant stress enough, that for something on this order of magnitude an interrupt would be better suited.
One of the rare cases where an interrupt is required.
50  Using Arduino / Programming Questions / Another timing answer on: September 22, 2014, 10:46:06 pm
As suggested by AWOL, above...Blink without delay, or http://forum.arduino.cc/index.php?topic=223286.0
51  Using Arduino / Project Guidance / Re: Vehicular emissions sensors ? on: September 22, 2014, 10:06:24 pm
Thank you, for the responses !

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Exhaust gasses, once they have passed through the silencer, possibly the catalytic converter and the rest of the exhaust system are not very hot, usually not above about 50°C.

That seems to be my concern. For example, this datasheet for CO sensor - MQ-7 - reports the operating temperature limit as -20°C to 50°C. Wouldn't that be cutting too close ?
Not if you do as I suggested above: "use a length of exposed (to cool air) metal tubing to take the gasses from the tail pipe, any excess heat will be dissipated by the time the gasses reach your sensors. "
I think that about 6 ft (2 Mtrs) would be sufficient, depending on the airflow and temperature around it. The tubing doesn't have to be straight!
52  Using Arduino / Project Guidance / Re: Coding help required on: September 22, 2014, 09:54:11 pm
You've posted your code (incorrectly) but haven't told us what the problem is.
There's no need to make another post to correct something, just modify (edit) your original post.
53  Using Arduino / Project Guidance / Re: Hygrometer Sensor Problems on: September 22, 2014, 08:14:05 pm
hello i am trying to make a simple project and get a value of the hydrogene in my room. It keeps returning 0...anyone knows why? :/I use D0 digital pins actually pin 3
You are trying to digitalRead an OUTPUT. It doesn't work, as you've found out.  Try digitalReading an INPUT.
An hygrometer measures the Specific Gravity of a liquid and has nothing to do with hydrogen gas.
If you've hydrogen gas in your bedroom, I hope you don't smoke.  smiley-eek
54  Community / Bar Sport / Re: Lead free solder on: September 21, 2014, 11:14:28 pm
It is not anecdotal it is there in the law. I don't think that they think it is pointless, like all stupid people they think they are doing good and protecting us. The problem is that they seem totally incapable of understanding the consequences of new legislation.
Recently they have said that they did not mean one law to have the result of prostituting people who sold food in imperial units. Yes that is exactly what is happening.
I think hope you meant 'prosecuting'.
55  Using Arduino / Programming Questions / Re: Avoiding Delay (blinkwithoutdelay) help on: September 21, 2014, 10:28:11 pm
I may be wrong, but I seem to remember reading that the microseconds counter is only updated every 4 micros. How then, can there be a measured 5 microsecond delay?
56  Using Arduino / Programming Questions / Re: DC Motor Spinning at 360 degree on: September 21, 2014, 10:10:54 pm
A normal DC motor will be very difficult to stop at exactly 360o, due to inertia, whatever method you use to detect when it has completed one revolution. I suggest you use a stepper motor.
57  Using Arduino / Programming Questions / Re: how to run sketches on my computer? on: September 21, 2014, 10:02:13 pm
There's also a 'ckunk' where I think he means 'chunk'.
58  Using Arduino / Project Guidance / Re: Vehicular emissions sensors ? on: September 21, 2014, 09:48:10 pm
Every UK garage that does MOT tests (required by law, every year, on vehicles over 3 years old) has a machine for measuring  exhaust emissions. It measures the CO, Hydrocarbons and the Lambda (whatever that is?).
A narrow metal tube is placed inside the exhaust tail pipe and the exhaust gasses are gently sucked through a 20 ft flexible tube to the machine. I suspect that the gasses, by the time they reach the machine, are sufficiently cooled so as not to be a problem.
If you use a length of exposed metal tubing to take the gasses from the tail pipe, any excess heat will be dissipated by the time the gasses reached your sensors. Your system will have to allow for any condensation that may form. I suggest using a peristaltic pump to suck the gasses.

Edit: Exhaust gasses, once they have passed through the silencer, possibly the catalytic converter and the rest of the exhaust system are not very hot, usually not above about 50oC.
59  Using Arduino / Project Guidance / Re: How to tackle curious project on: September 21, 2014, 09:07:03 pm
There's also LAN or ethernet over mains wiring, but in a large building it's likely that not all the sockets are on the same phase.
60  Using Arduino / Programming Questions / Re: Cannot See where I am going Wrong!! on: September 20, 2014, 08:32:41 pm
Once again
We see that you haven't read the forum rules for posting code. Always use code tags, the # button above the smileys.
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