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I received my second counter from Hobby Boards, but hooking up my gas-meter to it involved soldering some electronic parts together:



I had to do some experimenting as I found out that the sensitivity of the CNY70's detector decreases considerably when the distance to the reflecting object increases only by a few millimeters.

By experimenting with the values of some resistors I managed to get a reasonably well working circuit that outputs a pulse every time the digit '6' on my gas-meter comes around.

The circuit I built is a very simple voltage comparator, based on an LM324, a BC547 and some resistors. As soon as the voltage level on pin 3 is larger than the voltage level on pin 2 (adjustable by turning R1), the output of the LM324 will jump from 0 to 5V. The output of the transistor will then go from 5V to 0V. This is a trigger for the DS2423 to count a pulse (The counter in the DS2423 is triggered by a low-going signal).

I also found out that the CNY70 is very susceptible to daylight. If I open/close the fuse box the counter is increased by one. Also the exact positioning in front of the gas-meter is very important. A little off-center and the DS2423 does not count or increases by random numbers.

What do you think of this schematic:



Do you think there is room for improvement? Although I built a lot of electronic circuits, I am not very good at designing them ...

I am not measuring gas usage yet. First I will turn the experiment in something more definitive design. Then comes the rest (Counting / graphics).

24-4 edit: Changed schematic



Als het niet gerepareerd kan worden dan is het niet kapot!

[Joke mode on]
Looking at your soldering I wonder how you ever past your HAM license
[Joke mode off]

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Never start anything you can't fi

Obtaining a HAM license does not involve how to use a soldering iron. And besides, when experimenting, how you solder is of no importance. 99% of the time the circuit will be enclosed in a box ...

I sold all my home-build HAM radio stuff, so unfortunately I cannot show you what a well-built circuit looks like. But believe me, I can do better then what is shown in the picture [:)]
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by wifi</i>
<br />[Joke mode on]
Looking at your soldering I wonder how you ever past your HAM license
[Joke mode off]
--
Never start anything you can't fi
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">Als het niet gerepareerd kan worden dan is het niet kapot!

Hi Jfn,
Seems to me you may not have enough mA on the CNY70 emitter.
Data sheet for emitter IF 50mA VF 1.25V.
So 5 - 1.25 = 3.75V / 470 + 7.9mA
Try 150 ohms to get 25mA.
This may reduce the sensitivity to stray light & distance.
Malcolm T G3TCG

This was my gas monitoring schematic worked for 5 years, no problems with light changes what at all.
http://www.domoticaforum.eu/topic.asp?TOPIC_ID=111

@Malcolm T: I will try that. I also found out that the distance between the gas-meter and the CNY70 is important. Too close and I could not get it to work, too far and it also would not work.

In my schematic I will also be replacing R3 with a 470K variable resistor. I tried several fixed resistors and noticed that 1Mohm made counting too susceptible to daylight, and a low value (1K) did not make it count at all.

@Bwired: My schematic looks almost the same as yours. I added some extra resistors mainly for current-limiting (R2, R4). And I could not get your schematic to work with the DS2423 counter. The DS2423 should be open-collector, but without the pull-up resistor (R7) it would not count at all.

Btw, I added an extra resistor of 1M between the output of the opamp (1) and the + input (3) of the opamp to get the effect of hysteresis.

But to conclude this message, I have it counting gas-usage now. The influence of daylight when I open the fuse-box is zero. I will let it run for some time and in the meantime I can focus on other things.

Als het niet gerepareerd kan worden dan is het niet kapot!

Great, another counter in the can

Just a thought (and off topic), but did anyone here ever try some kind of OCR** for counting things like this?
(** Optical Character Recognition)

--
Never start anything you can't fi

Xemex has an optical meter reader which goes over the digits.



It is a major technological breakthrough in the field of Automated Meter Reading (AMR). This optical device is able to read digits at scheduled intervals or on demand. The product is compatible with most electricity, water or gas meters.
http://www.xemex.be/en/watchtalk_l32.htm

I tried mailing these guys a couple of years ago but they don't answer there mail at all.

Pieter Knuvers
www.bwired.nl Online House in the netherlands. Domotica, Home Automation.

Nice find Pieter,

Here is an other one: http://www.plexus-technology.com/V4US/P.php?n=55
Have a look at the demo (bottom of page)

--
Never start anything you can't fi

Looks very nice, and must work on our old gas/electricitymeter.
It has pulse output for the 1-wire counter

I have sent them an email, what it costs, including shipmnent

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by kroon040</i>
<br />Looks very nice, and must work on our old gas/electricitymeter.
It has pulse output for the 1-wire counter

I have sent them an email, what it costs, including shipmnent

<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">Please let us know if you get any info back.

--
Never start anything you can't fi

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Jfn</i>
<br />Btw, I added an extra resistor of 1M between the output of the opamp (1) and the + input (3) of the opamp to get the effect of hysteresis.<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">Can you update the schema? Thanks.

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by wifi</i>
<br /><blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by kroon040</i>
<br />Looks very nice, and must work on our old gas/electricitymeter.
It has pulse output for the 1-wire counter

I have sent them an email, what it costs, including shipmnent

<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">Please let us know if you get any info back.

--
Never start anything you can't fi
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

Yes I let know when I hear something of them.

Well here is the price for it

One OMR is quite expensive (the price reduces considerably for orders of 10+ OMRs).

The price for one OMR is:

Basic unit price - Euro 260
Connection device required to configure the OMR - Euro 25 (this can be used for multiple OMRs)
Pulse kit for each OMR device (this is a connector and tail leads) - Euro 6
Postage and Packaging - Euro 4

Total cost: Euro 295.


as you see pretty expensive