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Len sent in this great clock (schematic at the bottom of the site) - "It's actually a pretty simple circuit. The clock is based on an Atmel AT89C2051 microcontroller. The software in the microcontroller handles the count for the time. It "talks" to a 4 channel Digital to Analog converter to derive the voltage to position the needles on the three meters. The outputs of the D2A converters are buffered with a quad amp. Otherwise the current draw of the 1ma meters would exceed the D2A converter. A Dallas DS1307 generates an accurate 1hz timing signal and also backs up the time setting in the case of a power failure. It's very cool to watch the seconds meter raise as a minute progresses and them fall to zero again. The clock runs in a 24 hour mode." - Link.
The Meter clock
Posted by Phillip Torrone |
May 5, 2006 06:57 AM
DIY Projects, Electronics |
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I really like this project.
I have some questions though:
1)Why not use the microcontroller as the clock source? Get rid of the extra chip.
2)Why not use PWM to drive the meter and get rid of the D/A. Again, get rid of the extra chip.
The little bit of dithering noise on the PWM might look kind of cool on the meters.
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Drat! I was sketching out an almost identical project. I thought I had an original concept. The edge meters are nice, though. I was planning to use three vintage panel meters of widely ranging styles for a sort of 'cockpit' view. He's also managed to solve a couple of problems that were stumping me (like the buffering).
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Can someone post a link where I could purchase analogue meters like the one used in the project? Many thanks!
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I wanna build this too. I want to use some nice round panel meters, but...
Do they have to be 0-1ma meters? How much leeway do I have on the meter movements as far as resistance?
And matthew - post a schematic.
Reply to this comment
I wanna build this too. I want to use some nice round panel meters, but...
Do they have to be 0-1ma meters? How much leeway do I have on the meter movements as far as resistance?
And matthew - post a schematic.
Reply to this comment
I wanna build this too. I want to use some nice round panel meters, but...
Do they have to be 0-1ma meters? How much leeway do I have on the meter movements as far as resistance?
And matthew - post a schematic.
Reply to this comment
Didn't mean to do that 3x.
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I believe the style of meter used in this project is known as an "analog edgewise panel meter". That should be enough to get you started at Mouser or similar parts house.
Here is a similar meter clock project which looks like it does the pwm thing.
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