Future project Ideas

[andybarrett1]

Hi Thank you for reading

Am still looking at a future idea... Involving an old BT Telephone Mech.

I need the existing "Dial" to give me one digital pulse for each digit dialled..... :-

As I understand it at the moment the number 6 for example is dialled
As the dial rotates back to its rest position I will get a pulse train of six pulses ......Hi Hi Hi Hi Hi Hi ..... for 4 I will get four pulses as it rotates back ...Hi Hi Hi Hi.....etc
How might I convert these pulses into single pulses ... one for each digit dialled.

The BT Phone box (K6)in question is a UK listed landmark and needs to stay as authentic as possible.

Otherwise would just use PB switches

Help / Advice Welcome

BR
Andy

[pedja089]

Look in manual for COUNT.
Also you can start counting when another switch on rotary is closed.(It should be closed when rotary dial is moved from home position)

[andybarrett1]

Thank you pedja089

That might just do it :-)

BR
Andy

[mpgmike]

You could use a Timer that is set for a little longer than the span between pulses. Each pulse resets the timer and increments the counter. When the Timer times out, lock in your Counter as your number value and turn off the Timer. Loop waiting for a next incoming pulse, restart the Timer and start again. Have a second variable that increments with each saved value. If you normally use 7 digits (that would be a local call in the US), initiate the call after 7 number entries. You could also use a second timer that automatically dials when increments of 7 or 10 digits have been entered and the second Timer expires. As for the initiation of the dialing, I know there is a way to use TONEs to create dual tones (modern method of creating a number), but I don't know enough about telephone systems to know much more.

[Art]

You’ll need debounce which might as well be done is software. The probably eliminates using COUNT unless you do hardware debounce.
I never got a very reliable DTMF out of PBP, even with 20MHz crystal.
If you can go higher, you might get something decent out of DTMFOUT or FREQOUT.
I set the entire phone number to be dialled into an array, and output all of the DTMF at once after a period of inactivity of the dial.

There is also a HOME switch in the dial that is open whenever the dial isn’t in the home position that allows you to end your count
with confirmation that no more pulses are coming, and to look to start counting the next digit dialled.

[andybarrett1]

Thank you again all !!

Have already reasoned the de-bounce issue.... Old slow contacts, so fairly big unit of capacitance needed to dampen!

Also a Schmitt trigger to shape the final signal a bit better...All in hardware..... I am a hardware guy !

At moment ideas are in my pad and head... will be attempting breadboard soon.

Will keep you posted of progress.


Thank you all for input

BR
Andy

[Dave]

Andybarrett1, I would try an MC14490 hex debouncer.

[andybarrett1]

Hi Dave

I did see this chip ..... However the price is unreal as to a couple of caps / resistors and a Schmitt.

Question :-Would I need the Schmitt as the Inputs on most uChips seem to have one built in ?

BR
Andy

[Dave]

Then perhaps how about an MAX6816 or MAX6817?

[Art]

If you’re still talking about button input, Schmidt triggered inputs are only useful because you’re doing the debounce in hardware.
A Schmidt trigger input might help interpret a slope which is artefact of a capacitor you put there, but button bounce is square,
and alternates logic high and low, and is invisible to a Schmidt trigger.

We do this for logic, but when you’re looking at the port yourself, you ignore any high to low transition (or vice versa, depending how the button was set up)
for a duration after the last high to low transition you acted on. A software timer (loop counter) makes it a snap.

[CuriousOne]

It will be much easier, if you use these switch clicks to charge an capacitor, and measure it's voltage with ADC after. You have only 10 steps, so it will work just fine, no debouncing, no schmitt triggers and other yada yada.