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Old 9th Sep 2011, 2:47 pm   #101
mhennessy
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Default Re: 4 Digit Up/Down Counter IC?

Quote:
Originally Posted by jimmc101 View Post
I think there's a typo, shouldn't that be the 16F627A or 16F628A?
Quite right - thank you
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Old 9th Sep 2011, 4:12 pm   #102
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Default Re: 4 Digit Up/Down Counter IC?

Hello Mark,

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Originally Posted by mhennessy View Post
That does look rather challenging!
I didn't think it was too bad! I haven't examined it very closely yet, I'll find out when I do!

Quote:
I wonder if you could do something with the pulley that drives the original mechanical counter? Perhaps glue a slotted disc to it?
Yes, either that or the underside of the brake drum.

Quote:
Although there are some really good pictures in the manual, it's hard to get a sense of how much space there is when it's all assembled.
There's very little space between the motor and the chassis, not enough to fit in an encoder. From the top of the chassis to the underside of the brake drum is 1/2 an inch and to the underside of the top plate is about 3/4 of an inch. There would be enough space to fit the encoder.

Quote:
Presume you'll pick up the heater winding as a power supply?
Probably, I hadn't given a great deal of thought to that yet but there are three low voltage secondary windings from which I can choose: 24V, 22V and 12.6V. I think it will probably have to be the rectified 12.6V, the current drain isn't going to be very high so it shouldn't affect it adversely.

Regards,

Dave.
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Old 9th Sep 2011, 4:27 pm   #103
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Default Re: 4 Digit Up/Down Counter IC?

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Originally Posted by Amraduk View Post
Probably, I hadn't given a great deal of thought to that yet but there are three low voltage secondary windings from which I can choose: 24V, 22V and 12.6V. I think it will probably have to be the rectified 12.6V, the current drain isn't going to be very high so it shouldn't affect it adversely.
There is 6.3V as well - look to the top-left of the transformer.

But thanks for making me look more closely; I hadn't spotted that it uses a DC supply for the preamp valves. Very interesting

Either would be fine; the 12VAC would mean the voltage regulator runs a bit warm, but there's no shortage of metal to bolt it to. The 6V3 might be a little on the low side, but the PIC is happy down to quite low voltages, so you'll probably get away with it. Suck it and see

For the PSU and power-fail detect, the circuit used for my A4 amp is a good starting point (ignoring the capacitive dropper, of course, and drop the 10V Zener too). The IC would need to be a bit beefier than the 78L05, and you might want a larger smoothing capacitor. But that can be thought about later...

EDIT: Just looked again; the AC windings are 20-something volts, so disregard my mention of the 12VAC. And I'd be disinclined to use the 12V DC rail, because that is only 12V because 24V is being divided down by the valve heaters. The load added would upset the balance of the heater voltages (and possibly induce noise into the preamp). Looks like we should use the 6V3 AC winding
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Old 9th Sep 2011, 4:59 pm   #104
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Default Re: 4 Digit Up/Down Counter IC?

Hello Mark,

Quote:
Originally Posted by mhennessy View Post
There is 6.3V as well - look to the top-left of the transformer.
I had noticed that but I forgot to mention it!

Quote:
But thanks for making me look more closely; I hadn't spotted that it uses a DC supply for the preamp valves. Very interesting
Yes, clearly, they do it to eliminate hum from the heaters.

Quote:
For the PSU and power-fail detect, the circuit used for my A4 amp is a good starting point

EDIT: Just looked again; the AC windings are 20-something volts, so disregard my mention of the 12VAC.
Will do!

Quote:
And I'd be disinclined to use the 12V DC rail, because that is only 12V because 24V is being divided down by the valve heaters.
And you can disregard my mention of 12.6V DC! I had overlooked the fact that the ECC81's heaters are wired for 12.6V operation, giving 25.2V DC! I had added 2 x 6.3V giving 12.6V DC - or AC!

Regards,

Dave.
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Old 9th Sep 2011, 9:07 pm   #105
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Default Re: 4 Digit Up/Down Counter IC?

Hello Mark,

I was looking at the recorder's service manual and noticed that the counter is 3 digits, not 4 as I thought! What threw me was that a Revox B77 I have, does have a 4 digit counter, so I assumed the G36 was the same It's been so long since the recorder had one fitted that I'd forgotten it was only 3!

The 30mm x 7mm dimension applies the the 4 digit one, the 3 digit one measures about 22mm x 7mm. Also, the 3 digit one increments by one digit for about two revolutions of the spool. With a 2-segement encoder, that would give 4 pulses per digit, so that would need to be divided by four to give a reading equivalent to the mechanical counter.

If I can obtain a 4 digit seven segment display that will fit in the 22mm x 7mm 'window', then I'll still use 4 digits, otherwise it will be 3 digits.

Regards,

Dave.
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Old 9th Sep 2011, 9:46 pm   #106
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Default Re: 4 Digit Up/Down Counter IC?

Hi Dave,

No problem; 3 or 4 digits is easy (it's probably not worth modifying the code - just don't wire up the 4th unit). Dividing down is also easy - just let me know what you want (or have a go yourself )

Good luck find suck small 7-segment displays

Mark
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Old 9th Sep 2011, 11:42 pm   #107
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Default Re: 4 Digit Up/Down Counter IC?

Hello Mark,

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Originally Posted by mhennessy View Post
No problem; 3 or 4 digits is easy...
I thought it probably wouldn't make a lot of difference.

Quote:
...(it's probably not worth modifying the code - just don't wire up the 4th unit).
Do you mean the 4th seven-segment display (1000,s)? If the code is for 4 digits, the count would continue with that digit and it wouldn't roll-round to zero until the count reached 9999.

Suppose the count had reached (1)000 for the first time, the hidden count would be 1000, then every time the hidden count incremented by 1 (every 1000 counts), the visible count would be 000 but the hidden count would be: 2000, 3000, 4000, etc. up to (1)0000, equivalent to 0000. That doesn't seem right to me, or am I overlooking something?

Quote:
Dividing down is also easy - just let me know what you want (or have a go yourself )
Well, you've done all the work so far (in spite of saying you didn't have the time! ), so you may as well finish it! I can always play around with it afterwards.

Quote:
Good luck find suck small 7-segment displays
I found some 7-segment displays where four would have fitted in to the 30mm x 7mm window, so three should just fit in 22.5 mm, however, if I wanted to use four digits, I might have a problem finding small enough ones!

Regards,

Dave.
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Old 10th Sep 2011, 12:01 am   #108
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Default Re: 4 Digit Up/Down Counter IC?

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Originally Posted by Amraduk View Post
Do you mean the 4th seven-segment display (1000,s)? If the code is for 4 digits, the count would continue with that digit and it wouldn't roll-round to zero until the count reached 9999.

Suppose the count had reached (1)000 for the first time, the hidden count would be 1000, then every time the hidden count incremented by 1 (every 1000 counts), the visible count would be 000 but the hidden count would be: 2000, 3000, 4000, etc. up to (1)0000, equivalent to 0000. That doesn't seem right to me, or am I overlooking something?
Worry ye not

(0)998
(0)999
(1)000
(1)001
(1)002
...
(4)998
(4)999
(5)000
(5)001
(5)002

It's absolutely fine - honest. The old mechanical counter would have worked just as well if you'd covered up the left hand digit

Mark
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Old 10th Sep 2011, 12:40 am   #109
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Default Re: 4 Digit Up/Down Counter IC?

Hello Mark,

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Originally Posted by mhennessy View Post
It's absolutely fine - honest. The old mechanical counter would have worked just as well if you'd covered up the left hand digit
Yes, it would, however, the smaller the maximum count, the greater the chance that it will be exceeded before the end of a tape, under those conditions a count of n could be n +1000, n + 2000, n + 3000, etc. That was my concern (I should have made that clearer), so I think that it would be better to change the code to match the number of display digits.

Regards,

Dave.
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Old 10th Sep 2011, 1:17 am   #110
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Default Re: 4 Digit Up/Down Counter IC?

I can, of course, change the code for you, but I honestly don't understand your worry. The count rate and tape length determine how high the count will reach. Having the 4th digit invisibly counting away in the PIC will make no difference to the count rate. If you worry that the counter will exceed 999 on a single tape, we need to reduce the count rate, not remove the code for the 4th digit. You decide the count rate, based on the number of "slots" on your spinning disc. I can, of course, divide the count down for you if required...

Personally though, I still wouldn't worry. My first car had apparently only done 15,000 miles when I first got it. By simply looking at it, it was clear that it had really done 115,000 (old 5 digit odometer). In the same way, you can look at the spools to see where you are. It's a shame you don't have the old counter, because you'd be able to see if it "overflowed" with a full spool. As it is, although you might know the rotational speed of the reel table, do you know how that correlated to count rate with the original counter?

Cheers,

Mark
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Old 10th Sep 2011, 3:15 am   #111
Amraduk
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Default Re: 4 Digit Up/Down Counter IC?

Hello Mark,

Quote:
Originally Posted by mhennessy View Post
I can, of course, change the code for you,... If you worry that the counter will exceed 999 on a single tape, we need to reduce the count rate, not remove the code for the 4th digit.
I hadn't considered doing that. If the count rate was changed, then the count wouldn't match the mechanical counter. Perhaps the condition about which I was concerned won't actually happen.

Quote:
You decide the count rate, based on the number of "slots" on your spinning disc. I can, of course, divide the count down for you if required...
No, the encoder will produce 4 pulses per 2 revolutions of the shaft, that equals an increment of 1 on the mechanical counter, so, as previously mentioned, the encoder o/p needs to be divided by 4, so that 2 revolutions gives an increment of 1 on the electronic counter.

Quote:
It's a shame you don't have the old counter,...
But I do still have the old counter! Whatever made you think that I didn't? I never actually said that I didn't, I only said that it was broken.

Quote:
...because you'd be able to see if it "overflowed" with a full spool.
I never had a tape, even a 4500 feet one, exceed the maximum count of 999. And I realise that I've just demolished my argument about the 4th digit! I think I was thinking about the B77, I haven't run that long enough to see if the maximum count could be exceeded, though I'm beginning to doubt it.

Quote:
As it is, although you might know the rotational speed of the reel table, do you know how that correlated to count rate with the original counter?
Yes, I wouldn't have been able to give the count increment per revolution of the shaft if I didn't!

Why not pretend that I never mentioned it and leave things as they are? Sorry for the drama!

Regards,

Dave.
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Old 10th Sep 2011, 9:50 am   #112
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Default Re: 4 Digit Up/Down Counter IC?

No problem - all understood

Mark
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Old 12th Sep 2011, 5:23 pm   #113
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Default Re: 4 Digit Up/Down Counter IC?

To get the count to survive power failures, you will need a large electrolytic capacitor across the PIC, big enough to store enough energy to keep it going long enough to write the EPROM, and wired via a diode so the only thing that can draw any current from the cap is the PIC itself; and an input, driven from the power transformer, upstream of the rectifier and smoothing can, to indicate that mains is present. After a few missed mains cycles, but before the capacitor is too depleted to keep the p alive, write the present count value to E. On power-up reset, read the value from E.

If you have another I/O line to spare, you could even assert it when all four digits are zero. This could then be used to disengage the mechanism solenoid, so providing a "memory" function as found on some VCRs.
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Old 12th Sep 2011, 11:45 pm   #114
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Default Re: 4 Digit Up/Down Counter IC?

If its any use to you, I can offer a PCB with 3x HDSP-F303 (+2x HDSP-F503) Fig-8 displays, these are about 9mm wide by 13mm tall each. They will be wired in parallel on the PCB, but they could be removed or the PCB could be cut down to suit.

Yours FOC, if any use.

Dave.
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Old 13th Sep 2011, 1:29 am   #115
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Default Re: 4 Digit Up/Down Counter IC?

Hello Dave,

Quote:
Originally Posted by davegsm82 View Post
If its any use to you, I can offer a PCB with 3x HDSP-F303 (+2x HDSP-F503) Fig-8 displays, these are about 9mm wide by 13mm tall each. They will be wired in parallel on the PCB, but they could be removed or the PCB could be cut down to suit.Dave.
Thank you very much for your offer, that's very kind of you.

I'm afraid they would not be suitable for my application because the are too large, the actual display size is 10mm high but the 'window' through which they would be seen is only 7mm high. Also, they're yellow coloured, which I don't particularly care for!

Maplin have a suitable display which is 7mm high and is very reasonably priced, so I may get those.

Thanks again for your offer.

Regards,

Dave.
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Old 13th Sep 2011, 7:57 am   #116
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Default Re: 4 Digit Up/Down Counter IC?

No problem, I just happened upon them in a junk box last night, I thought they might be a little too large.

Dave.
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Old 19th Sep 2011, 12:56 pm   #117
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Default Re: 4 Digit Up/Down Counter IC?

Just found the device I initially wanted to recommend, it is 6 digit though and needs an external battery for retention but at 5uA should last for quite some time!
It is the TRUMETER 7000AS avaliable here for less than 14 +VAT.
http://www.countersales.co.uk/produc...FcMKfAod_0C50Q
The info sheet on it is at:
http://www.countersales.co.uk/datash...SDatasheet.pdf
I have used these as timers in the past, feeding them with a gated stream of 100ms pulses then resetting after a read time before gating again. This was for battery operated equipment. Not used the 7000AS Bi-directional model myself but I am tempted to get one myself for experimenting with.
Les
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Old 19th Sep 2011, 8:27 pm   #118
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Default Re: 4 Digit Up/Down Counter IC?

Hello Les,

Thanks for the information about the Truemeter counters - 15.84 plus carriage, whatever that is! I don't think the cost difference between one of those counters and doing it with a PIC is going to be very much, so no great advantage there.

I will be using only three digits (that being all that can be seen through the counter 'window'), so half of one of those counters would be wasted! Also, the digits are quite close together which might make fitting it with only three digits showing difficult, as part of the fourth may be visible, if the digits weren't sloping, it would be a bit easier.

Doing it with a PIC would eliminate the need for a battery to retain the count, I realise the Truemeter current drain is very small, but I would rather not use a battery, if at all possible. Overall, I think doing it with a PIC will be better, and it leaves open options for other features, which wouldn't be the case with one of the Truemeter counters.

Thank you for taking the trouble to provide that information.

Regards,

Dave.
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Old 7th Apr 2013, 12:57 am   #119
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Default Re: 4 Digit Up/Down Counter IC?

Hello Amraduk,

I just came across this thread and I had the same idea with my Revox reel to reel machine.
A repair service for Revox tape maschines here in Germany is selling such a counter based on a PIC 16F628 - unfortunatley quite expensive (119 euros).
The rotations of the capstan motor are detected by two IR-phototransistors and the value of the 4digit counter is stored in the eeprom of the PIC when the power is switched off (using a large cap, as described here in ajs_derby's posting).
http://www.revox-bandmaschine.com/zaehler_77.htm

To use this counter instead of the mechanical one you have to enlarge the window on the front panel, what I wouldn't do. But I found very tiny 0.2 inch LED displays (what might interest you too) here:

http://www.kingbright.com/product_ma...20050525051040

What about your counter? Is it finished and working yet?

Best regards,
Bernd
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Old 10th Apr 2013, 10:25 am   #120
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Default Re: 4 Digit Up/Down Counter IC?

Hi
Not sure about the input required but I have a ZN1040E if you want it?
http://www.harrisonelectronics.co.uk...ts/ZN1040E.pdf

Chris
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