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Looking for Datasheet on old Texas Instruments strobed Digital Clock Chip, M35020

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globecollector

Jun 27, 2011
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I have a digital clock, (taken from a space heater) which is built around the T.I. M35020 clock chip which has strobed display and buttons...in this application it also takes in basic data from an LM339 from thermistors and outputs data to control relays and TRIACS for the heater...none of which I need to use.

I wish to Re-purpose it as a battery capacity measuring device for Electric Vehicle 7.2v six-cell Ni-MH batteries, where they are discharged into a 1A constant current sink and a comarator "watches" the voltage...as soon as the first cell is flat the c 300mV drop will trip the comparator, disconnect the current sink and stop the clock (but hold the number on the display), which will then read the battery capacity directly.

The clock chip has its own 400KHz ceramic resonator oscillator, but also takes in 50Hz reference from the mains. When the mains is on the 50Hz gates the strobing of the chip and is somehow locked to the 400KHz oscillator, possibly by a P.L.L. inside the chip.

I have fed other frequencies into the 50Hz input, at 10Hz, the display strobes slowly from MSB to LSB of the display and it runs five times slower...as expected. Up to 5KHz it simply strobes faster but works (at norlmal rate) only at some frequencies which presumably lock to the oscillator and at others where lock is not possible it just sort of stops randomly with one seven seg lit up. If the 400KHz oscillator is stopped it can do a multitude of things depending where in the strobing cycle it stopped and how many times the 470nF capacitor I was dabbing between the output side of the resonator and ground "bounced", sometimes it comes back with no change, but the display goes blank when the 400KHz goes, sometimes it latches up, sometomes it comes back with an advanced count.

There are at least four strobed output lines and five strobed input lines with buttons or switches at some intersections, but other intersections are ominously empty and others receive data from the 339 by some clever tomfoolery with pull up resistors to selected strobed output lines...I suspect the "stop watch" function may well lie at one of those unused intersections, but I really need the chip's datasheet for that...AND, for those who thinkGoogle Knows Everything, well not about the M35020 it doesn't!
 

kellys_eye

Jun 25, 2010
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Seems rather an antiquated (although perfectly reasonable) way to do what you're doing - until the device you're using goes mammaries skywards and there are no replacements to be had.

A battery operated analogue clock with a simple switch in series with the battery would seem a much easier solution (I always advance the KISS principle).

However, I shall dig out my old TI reference books and see what I can find......
 

globecollector

Jun 27, 2011
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Thanks, it would be appreciated. I chucked most of my data books when I moved house. Kept just NS Linear a Philips HEF4000 Logic and Motorola Linear book. Ironically these seem to be the easiest to find online...but who ever made such a rational decision under the pressures of a house move.

Agreed, there are simpler methods, as you say, but it requires procuring stuff, this stuff, I have right here on the bench.
 

globecollector

Jun 27, 2011
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Further Developments, found another digital clock similar, this one has the non-strobed MK50375N clock chip in it, again, Mr. Google seems to have "forgotten" this one too....any success finding those databooks?
 

globecollector

Jun 27, 2011
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Problem solved! The The MK50375 is a really logical and simple to use chip. It can drive V.F.D. displays or Seven Segment L.E.D. There is no crystal reference oscillator, phase locked loops or strobing guf. It simply takes the 50Hz (square wave) in on pin 30 via a 1N4148 with the cathode facing out, (so it's some sort of pull-down) . There are a few other pins for "set-the-time" buttons and two programmed timer outputs and that's it!

In this case it is driving a V.F.Display so I thought I needed low voltage A.C. for the heater/cathode, but there is a rectifier for that and it is run off 2.8v D.C. @ c80-100mA, so I was rough as guts and just dropped it from the 12v rail via a 110 Ohm 2W resistor. Bumped up the current consumption from 20mA to around 100mA, but who cares, those batteries contain power to burn anyway.

The BIG PLUS is, when the 50Hz is stopped in the low state, the display freezes...Exactly what I am after! AND, I found two of them, so I can do two batteries at once and get them all done twice as fast.

Test running it from the signal generator demonstrates that it still works with 500Hz in, although it goes a bit silly up near and beyond 1KHz, really funny to see it cranking along with 500Hz in.

I thought I would put this post so others might gain something by reading it and as I noticed not many others seem to post when (or if) their problems are resolved and reach some conclusion of just remain unsolved.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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If there is any scanned documentation it would be really handy if you uploaded it here. You can give the internet some of the stuff is forgotten.
 

globecollector

Jun 27, 2011
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Unfortunately I turfed most on my data books when I moved to a smaller house. I had a mate with a big workshop in the basement of the Chemistry Department at the University of Tasmania, he was the last tech standing and had gone from working on N.M.R. machines to fixing photocopiers. He recently retired and most of his workshop was turfed, including two bookcases of data books. There was so much stuff it has been appearing in at the tip shops for months. The University seems to be heading toward being a "paper" university with just more bums-on-seats in front of computers....as a society we must be careful we don't inadvertently "lobotomize" ourselves, and all this movement from libraries to date centres is a step in that direction.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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He recently retired and most of his workshop was turfed, including two bookcases of data books.

Aaaaaagh!

There was so much stuff it has been appearing in at the tip shops for months.

I have this almost irresistible urge to travel to Tasmania for a "Tip Shop tour".
 

uawahrani

May 27, 2024
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I have a digital clock, (taken from a space heater) which is built around the T.I. M35020 clock chip which has strobed display and buttons...in this application it also takes in basic data from an LM339 from thermistors and outputs data to control relays and TRIACS for the heater...none of which I need to use.

I wish to Re-purpose it as a battery capacity measuring device for Electric Vehicle 7.2v six-cell Ni-MH batteries, where they are discharged into a 1A constant current sink and a comarator "watches" the voltage...as soon as the first cell is flat the c 300mV drop will trip the comparator, disconnect the current sink and stop the clock (but hold the number on the display), which will then read the battery capacity directly.

The clock chip has its own 400KHz ceramic resonator oscillator, but also takes in 50Hz reference from the mains. When the mains is on the 50Hz gates the strobing of the chip and is somehow locked to the 400KHz oscillator, possibly by a P.L.L. inside the chip.

I have fed other frequencies into the 50Hz input, at 10Hz, the display strobes slowly from MSB to LSB of the display and it runs five times slower...as expected. Up to 5KHz it simply strobes faster but works (at norlmal rate) only at some frequencies which presumably lock to the oscillator and at others where lock is not possible it just sort of stops randomly with one seven seg lit up. If the 400KHz oscillator is stopped it can do a multitude of things depending where in the strobing cycle it stopped and how many times the 470nF capacitor I was dabbing between the output side of the resonator and ground "bounced", sometimes it comes back with no change, but the display goes blank when the 400KHz goes, sometimes it latches up, sometomes it comes back with an advanced count.

There are at least four strobed output lines and five strobed input lines with buttons or switches at some intersections, but other intersections are ominously empty and others receive data from the 339 by some clever tomfoolery with pull up resistors to selected strobed output lines...I suspect the "stop watch" function may well lie at one of those unused intersections, but I really need the chip's datasheet for that...AND, for those who thinkGoogle Knows Everything, well not about the M35020 it doesn't!
To repurpose your digital clock built around the T.I. M35020 clock chip as a battery capacity measuring device, follow these steps:
  1. Frequency Adjustment:
    • Since the chip responds to different input frequencies, provide a consistent and appropriate reference frequency (likely 50Hz) to maintain accurate timing.
  2. Current Sink and Comparator:
    • Use a constant current sink circuit to discharge the battery at 1A.
    • Connect a comparator circuit to monitor the battery voltage. The comparator should be set to trip when the voltage drops by about 300mV (indicating the first cell is flat).
  3. Clock Control:
    • Integrate the comparator output with the clock's control mechanism. When the comparator trips, it should trigger a signal that stops the clock chip.
    • Ensure the signal holds the display value upon stopping the clock to read the battery capacity directly.
  4. Strobe and Button Inputs:
    • Identify the strobe lines and button input lines on the clock chip. Experiment with connecting the comparator output to these lines to find a configuration that stops the clock as needed.
    • Use pull-up or pull-down resistors as necessary to ensure the signal is correctly interpreted by the clock chip.
  5. Testing and Calibration:
    • Test the setup with a known capacity battery to calibrate the system. Adjust the reference frequency and comparator settings as needed to ensure accurate readings.
This approach leverages your existing hardware and avoids the need for a detailed datasheet by relying on experimentation and testing to achieve the desired functionality.


4o
 
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