Bit of a puzzle

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Lenp
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Bit of a puzzle

Post by Lenp »

I have serviced several counters self contained that use a 3.3v 7500ma Lithium 'D' size cell, a refelective pickup, and a a large .75" LCD display. The battery replacement is all that is ever needed and they last almost 4 years.
The counter uses a photo reflective pickup, has no power switch, and the sensor is always connected.

The puzzle is, what is the technique to the low battery drain?
The lowest current LED I could find is 2ma and, that is way more ampere hours than the battery could supply for that long of a time, neglecting the processor and other support chips load.

These are not new technology. probably at least 15 years old!
Here is the manufacturer's link http://mollbrothers.com/product/counters/
Any ideas?
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)
dyarker
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Re: Bit of a puzzle

Post by dyarker »

Is there a trigger switch? (Pres or squeeze to do a count.)

My EWAG is that everything is off till trigger, circuits inside boot, light LED, do count, store result in static RAM; and power down again. Whole process under a second.
Dale Y
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Lenp
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Re: Bit of a puzzle

Post by Lenp »

Hi Dale,
Nope, no trigger switch

It is 'point and count', the control has a rate / count switch and a reset switch

The sensor is potted, with an IR LED, a photo transistor and a magnet for mounting. The count or rate remains on the counter until reset.
I inderstand this model has been discontinued a few years ago.

Thanks for your input!
Len
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)
dyarker
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Re: Bit of a puzzle

Post by dyarker »

I inderstand this model has been discontinued a few years ago.
Yeah, worked too well! They couldn't sell a replacement battery every 6 months, hee, hee.
Dale Y
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Lenp
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Re: Bit of a puzzle

Post by Lenp »

The next time one comes in I'll make a list of the IC's and get a few measurements to see if I can unravel this mystery.
I think there were some 7400 series IC's and they certainly were not low power by today's standards.
I'll revisit this later when the information is obtained...But it may take four years :shock:
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)
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haklesup
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Re: Bit of a puzzle

Post by haklesup »

LCD is inherently low current to begin with. If the controller associated with the display (glass) is also optimized for low current then the whole thing can last a long time. Consider that LCD glass portion of the display basically takes no current, all you need to do is produce an electric field between two plates and the crystals line up and block polarized light. The segments are typically just metalized traces on the glass surface and the back plate is a ground plane.

There are numerous modern microcontrollers that use extremely low current. See Atmel, Microchip etc, they all have some parts optimized for extremely low power and if you select a part that just does what you need for a counter then I can see this lasting a very long time. My calculator only needs a change every few years and I use it daily (it is 30 years old now TI-35 plus).

The IR LED could consume a bit more power than other parts of the circuit but if the pulse were kept short, there is plenty of opportunity to optimize. For example 1us every 10ms would probably be ok for counting and be very miserly on power.

While the 7400 and 74LS00 parts consumed several mA static, the 74HCT00 and 74ACT00 CMOS parts consume nA when static and briefly 3mA when switching. Combinational logic CMOS was consuming low power 40 years ago with 74HC and 4000 series logic devices but dynamic power has been going down continuously. Anything that clocks or has many state changes, those dynamic events are where power is used in CMOS devices.
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Lenp
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Re: Bit of a puzzle

Post by Lenp »

Well, that helps unravel some of the mystery.
I still think there's some reason they stopped making them, like maybe a custom LSI that is no longer fabricated. If it was all 'standard' parts it probably could still be profitably produced.

Thanks,
Len
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)
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haklesup
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Re: Bit of a puzzle

Post by haklesup »

probably far more mundane than that like the seller did not reorder from the manufacturer or like so many products (in bins during Christmas), it was a one hit wonder where they made a bunch and never intended to make more just like it. 10 to 15 years ago, retailers were taking more risks with electronics products than they seem to now. Certainly if a manufacturer wanted to build 10k more, an order like that would be filled by a chip maker even if the part were in the "not for new designs" or "obsolete" category. money talks.

Indeed I did not find any event counters with optical pickup outside the industrial solutions. There are a lot more choices in event times with LCD display but none with optical triggers that I could find. I wonder if there is a App for that.
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