Hello.
This is my first post on this forum and I'm looking for some advice or direction. I have one of those projects in mind that many would say, "why bother" but I'm hooked on finding a solution. I don't have advanced skills in electronics; I've built quite a few small kits and nutted out simple things but don't have the knowledge to work out a solution on my own.

Firstly, I have spent a couple of days trying to google exactly what I'm looking for, and have on a couple of occasions come close, but not exactly.

What I'm trying to do is this: I have a very fine old TEAC reel-to-reel tape deck that I would like to replace the analogue tape counter with an LED digital one. My thinking was to use the opto interrupter as used in an old ball mouse, which would be fixed to the driven pulley of the mechanical counter, that would provide the pulse for a 4 digit display. I have a 0.28" 4 digit array that will fit neatly in the existing space.

The problem I have is finding an example that would function in the way required. The replacement needs to act in the following way.

Counter will increment in one direction from 0000 to 9999 and then roll over back to 0000. It needs to be able to decrease in the same manner when the deck is in rewind. It also needs a reset function to return it to 0000 at any time a button is pressed.

This doesn't need to be sophisticated, linked to actual feet of tape or even duration, so long as it provides a point of reference.

I've bought a 4 digit digital counter from eBay but am unsure whether this will behave in the way I need, and unsure of how to make it function with the opto sensor.

I have so little knowledge in this area that the sensible suggestion would be don't bother, but I'd really like to try. I just need someone who can give this a little thought and explain it to me at idiot level.

Thanks everyone. Hope there's someone out there who'll take pity. Cheers, Wayne

 

hi wj,
Welcome to AAC.
Post a link to the counter on eBay, we can look at the specification.
E

 

Is this what you mean by an "analog" counter:


If not, do you have a picture of yours and how it is driven?

 

I would call that a mechanical digital counter.
You need to Google "quadrature counter" as this is what you need to interface with a quadrature encoder. (Which this is what the encoders used in mice are.)

Les.

 

Hello,

Do you have a link to the mentioned counter?
It should be able to count up and down and have a reset, as you descibed.
Also the mentioned sensor should be able to sense the direction of motion.
Do you have more details about the sensor?

Bertus

 

@LesJones

I have two versions that look almost identical on a panel. One is incremented by an eletrical impulse; the other is driven by a friction wheel/capstan like an old fashion odometer. The former would be really easy to implement. The latter would be a little more difficult. I would consider something like a rotary encoder, possibly a mechanical or optical, low-resolution one.

That is why I asked how it was driven

 

Hi everyone. wow, I didn't expect the flurry of responses so quickly. Thank you all for taking the time.

To address your questions, the deck is a TEAC X-10R which has an old 'odometer' style counter. Here's what it looks like.





The counter module I bought from eBay is item number 201800504526 and looks like this:



My plan was, if this module functions the way I need, to attach an opto interrupter (if that's what it's correct name is) as used in a trackball mouse, to the outer face of the driven pulley and passing through the sensor. The wires coming from the counter in the photo link to a timer module which I won't be using and can be disregarded.

Thanks so much for everyone's input. I know it must be frustrating when trying to help someone with as little knowledge as me.

Cheers all, Wayne

 

I assume that on the original mechanical counter that there is a set of contacts that open (Or close) when the count reaches zero. Am I correct. Also is that is that a second pair of wires connecting to the back of the counter and if so what do they do ? I don't think the counter in the link will do what you need. The information does not say how the count up/cont down is controlled. You would require a counter with two input from a quadrature encoder. (A quadrature encoder has two outputs 90 degrees phase difference so you know if the count needs to increment or decrement depending on the direction of rotation. If you only have a single pulse you do not know if the count needs to increment or decrement.) You also require an input to set the count to zero and an output signal to stop the motors. You also need two wires for power supply so you need at least six wires. The picture only show four wires.

Les.

 

Hi Les,
I realised that the photo of the mechanical counter may be a bit misleading. There are only two wires coming from it, but they have been looped around in the photo giving the impression there's four wires.

The two wires are a simple switch that works in conjunction with a timer function that I will never use. If I can replace the mechanical mechanism with an LED display I won't be utilizing that function. The main reason I'm doing this, apart from being a compulsive challenge, is that my eyesight isn't good enough to easily read the old odometer style counter. The numbers that will be displayed on the LED will not have to have any other purpose than being a point of reference to find approximately the same place on the tape.

Piggy-backing off the drive pulley as I'm proposing should provide as repeatable a result as the original mechanical device.

As for the eBay counter, I wasn't sure if it was going to suit as the description wasn't particularly detailed. As it was fairly cheap I took a punt and ordered it, with a view to having it located remotely within the cabinet and a smaller 4 digit display (0.28 inch) tapped in to replace the existing 0.56" one. I'm assuming they should be wired the same so long as I maintain either common cathode or anode.

The eBay counter does have six terminals on the back in a four and two arrangement. The separate two pin header is for the signal in.

Cheers, Wayne

 

You still don't seem to understand that from a single pulse you do not know if the count should increment or decrement.

Les.

 

Yes I know, and that's where I need help understanding how to do this.

Wayne

 

Here is a link to an explanation of quadrature encoders. You will find that the encoder disks found in a ball type mouse has two sensors on each encoder wheel. You can also find quadrature rotary encoders in printers. Using a microcontroller is probably the easiest way to covert the signals from a quadrature to a counter type display. I can give the source code to display the count from a quadrature encoder on a 2 x 16 LCD display. This code is for a PIC16F690. You would need to modify it to use 7 segment LEDs in place of the LCD display.

Les.

 

Many thanks Les. I'll follow up on that link and the code for the PIC would be a useful start. I do have a PIC encoder for that type.

Cheers,
Wayne

 

The mechanical counter will retain its Reading on Power Off condition.
The Electronic one will not, unless some Non Volatile memory is used.

 

A PIC has built in EEPROM that could be used to store the count when it detects loss of power. This would require adittional circuitry to detect loss of power to tell the PIC to store the count. It would also require a capacitor to keep the PIC powered long enough to stor the count.

Les.