Author Topic: I only make prototypes :-) Payphone controller  (Read 3373 times)

Offline dsk

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I only make prototypes :-) Payphone controller
« on: May 31, 2014, 12:12:14 PM »
I only make prototypes!
It is because I only need one.

This was not easy, I have ruined some relays, so now what you shod not do after me:
1 A line sense relay of reed relay type does not handle enough current to power a huge relay with capacitor. (burned 2)
A normal telephone relay may have trouble handling higher voltage to the collect/return relay.

So I started from scratch with whatever I had in the basement.

dsk

Offline dsk

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Re: I only make prototypes :-) Payphone controller
« Reply #1 on: May 31, 2014, 12:45:12 PM »
How may I  sense the off hook state?
I put in a solid state relay, and with a rectifier and a resistor it do not cause to high voltage drop, and are not polarity sensitive.

I t might be a "slightly overkill" to use a 75 Amp relay, but it was what I had, and I have no other use for it. It powers the entire circuit so it does not use any power at all in on hook position.  Then I needed a relay, and what I had with huge solid contact sets was a 24 volt relay without the proper socket. (so I just soldered). Yes It worked with several power supplies, but I needed a suitable voltage for the 100V relay. After some experimenting I ended up with the center tap of the primary on the transformer. (If you have 120V mains, you may safely use it!) The 120V are slightly to much, but an easy choice.  A diode and a resistor limits the current drawn, and rectifies good enough to charge a 470V capacitor to nearly 150V (It needs more than 10 sec to charge enough)
The 91 kilo-ohms resistor discharges the capacitor if the circuit are not connected, broken or...
To cope with the far to high voltage, I just let the voltage drop over a 1000 ohms resistor.

The next step will be to get a system for automatic selecting between collect or return. but that will come later.

part 1: Solid state relay (Tough opto-coupler)
2: 115+115V to 9+9V transformer. (with a rectifier soldered direct to the 18 V)
3: 24 Volt relay.
4: Resistor shunting the input of the solid state relay to keep voltage drop low.
5: Rectifier
6: 2x 470 microfarad capacitor for delay after hang up.  (take what you have to get 2-3 sec delay)
7: 1000 ohm resistor to generate voltage drop when collecting/returning money.
8: capacitor supplies energy for collect/return relay.


dsk
« Last Edit: May 31, 2014, 01:28:01 PM by dsk »

Offline WesternElectricBen

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Re: I only make prototypes :-) Payphone controller
« Reply #2 on: May 31, 2014, 01:25:40 PM »
So... Did your prototype even with the catch ups and the knowledge needed still top the official payphone controller, or do you still recommend buying one, if you have the funds?

Ben

Offline dsk

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Re: I only make prototypes :-) Payphone controller
« Reply #3 on: May 31, 2014, 01:38:59 PM »
I guess the professionally made controllers are better, not take what ever you have, and do the best out of it.
It is definitely smaller, and optimized in every hence.

My next step will be to find a way to detect answer in the other end, so far reverse polarity on an analog telephone adapter are my only choice.

The ones in sale just have a timer, when you have been off hook for a sudden time (do not know how long) it changes from return to collect.)

It is not only a matter of money, it is a matter of cope with it my-selves, really understand how it works.


dsk
« Last Edit: May 31, 2014, 01:42:00 PM by dsk »

Offline dsk

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Re: I only make prototypes :-) Payphone controller
« Reply #4 on: June 12, 2014, 01:46:19 PM »
Really fun, so I have got an DC/DC optocoupler, and changed the circuit. Now it collects if party answers, and returns if not.

Comments and picture under.

dsk

  1-2 Line from ATA who change polarity when party answers.
3-4 Mains (230V have need for center tapped primary on transformer)
5-6 Line to payphone.
7-8 Line to coin relay.
Rectifiers and diodes: most will due.
A Optocoupler DC/AC  (polarity sensitive input)
B Optocoupler DC/DC (polarity sensitive)
Transformer with rectifier, mains to 24V DC.
C and C1: 24V relay and capacitor to hold for 2-4 seconds. (2 changing contacts)
D and C2: 24V relay, with capacitor to hold at least 1 sec longer than C. (2changing contacts   1 closing to hold relay).
Resistors:
 r1 shunts circuit in hence to keep suitable voltage drop 220 ohms works for me.
 r2 limits current during charging of C3 (6700 ohms allows charging within 10 sec)
 r3 discharges C3 if no load applied 91 k ohms used.
 r4 optional 1000 ohms limits current. Value must be tested.
C3 150uF 400V works for me.
 
Notes:
 All values are approximately based on prototype building. Parts used are pretty random just because it is what I have.  r1 and r2 should not be rated less than watts. Capacitors should be rated at least double voltage of what you read on your meter.
This circuit could probably be expanded with timers and decoders for paying at intervals, her you pay just once.
The telephone may not send dial tones on reverse polarity, if needed rectifier and moving ringer circuit to before rectifier may be an option.
 
Dsk 12. June 2014
 

Offline dsk

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Re: I only make prototypes :-) Payphone controller
« Reply #5 on: June 12, 2014, 02:23:52 PM »
Here are my rectifier and ringer solution.
The rectifier gives - to ring, and   to tip.
The yellow and black from controller goes directly to ground (Yellow on phone) and to tip (green on phone) The line are splitted and goes to the ringer via a 1/2 uF capacitor.

I have chosen to feed the coin relay in separate wires to the phone to not risk any "back-streem" current on the line.
This makes it easier to apply the rectifier to.

dsk

Offline Kimball321

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Re: I only make prototypes :-) Payphone controller
« Reply #6 on: July 23, 2014, 10:58:52 PM »
I know this topic is a bit old but dose this controller give dial tone before money is inserted, and dose it have a method of allowing "free" calls (911, 1-800 ect) without coins?
I collect payphones :)

Offline dsk

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Re: I only make prototypes :-) Payphone controller
« Reply #7 on: July 24, 2014, 02:43:01 AM »
Yes, you get the dial tone (from the ATA), and no, no free calls, the telephone it selves does not allow the dial to work before money are deposited.

dsk
« Last Edit: July 24, 2014, 02:48:49 AM by dsk »

Offline dsk

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Re: I only make prototypes :-) Payphone controller
« Reply #8 on: May 15, 2016, 07:58:45 AM »
A liitle difficult to get the links in when answering from phone, but a link in the thread I linked to describes my coin controller. It works, and did not cost to much.  Since you have differen mains voltage, you may choose another transformer.
dsk

Offline dsk

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Re: I only make prototypes :-) Payphone controller
« Reply #9 on: June 06, 2016, 08:50:36 AM »
After long time testing, this seems to be working, and stable so I did mofdyfy the chematics to fit North Amercan systems. So by using a 120 to 24V transformer, this should work:

As usual; on your own risk. I will contain mains voltage, and even more in DC. Charging the capacitor with more than 1  Joule but still less energy than in an average electric fence box.

dsk

Offline robert_m

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Re: I only make prototypes :-) Payphone controller
« Reply #10 on: December 06, 2018, 02:42:20 PM »
You have one you want to sell?  I've been using Stans controll, but it has died and he no longer makes them, so I've been told, nor has any left.

Offline dsk

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Re: I only make prototypes :-) Payphone controller
« Reply #11 on: December 06, 2018, 03:25:02 PM »
I'm sorry, I just made this of parts I had, and it is a pretty huge box with parts glued in. It wiould probably not be good enough to send over the pond, and shipping from Norway would be approx $64 so that would be an expensive and risky project. 

I guess you could build one after the schematics in this thread, and it is just working if you connect it to an ATA who switch polarity when party answers.

dsk


PS these links may be of interest:   http://oldphoneguy.net/images/WordConv2PDF2.pdf
http://oldphoneguy.net/
DS


« Last Edit: December 06, 2018, 03:32:40 PM by dsk »