I have a Telephone Interface Project designs in Eagle Cad 6.5+ PCB's using only Transistor logic and possibly hall effect chip; opto-isolation, resistors, diodes and capacitors thoughole componets. May also want to include 555 timer circuit to time out relay contact if phone is not answered. 5v will be used to power a Spark Core MCU which uses [url removed, login to view] for Digital / Analog pins. Status of phone line condition "No Power" / "ON-HOOK" / "OFF-HOOK" / Powered - Waiting For Call = Isolated from GRID will need to be referenced back to the Spark Core MCU as Analog or Digital. (Spark Core IDE Coding will not be part of this project as I will do initail interfacing wit software for testing purposes).
There will be two separage circuits / boards. The first circuit / pcb board requires the use of Induction non-contact pickup (insulated wire wrapped around one telephone wire) to detect the 90VAC ring signal. It will then turn on a Relay to connect the phoneline to my home so my phone rings. The second circuit board WILL NOT be part of this project and it will contain the Spark Core MCU.
The purpose of this project is to provide isolation for my home wires so I can use them for other purposes while waiting for a call.
How it should work subject to your recommendations:
Power is applied to circuit and a relay (5v most likely) is held open waiting for a phone call to come in to my home.
If I do not answer the phone, the relay will time out and open contacts (resets) to wait for another call.
If I do answer the phone the relay latches and contacts and will remain closed until I hang up the phone.
When I hang up the phone the relay contacts will open back to waiting for a call.
Some Specifics on Design Requirements:
1. I would like to use a Ferrel Core Bar with telephone wire wrapped around it and a Hall Effect Sensor to detect the -48VDC "ON-HOOK" state. If this is possible the whole device would be Non Contact and I would not be violating FCC rules.
2. If 1. above design does not work, another option to pickup the -48VDC state would be a non-contact hall effect chip current sensor that will sense 20mA like these I(Or similar)
[url removed, login to view]
3. If by any chance both 1. and 2. and Non Contact Sensing of the -48VDC is not possible, sensing of both 90VAC Ring and -48VDC "ON HOOK" will be done by contact of telephone wires and will need to be within 4. below parameters.
4. If contact is made to copper telephone wires the circuit must be:
A. At least 800 Ohm Resistance;
B. Total load of 20mA;
C. Final pcb will be no more than 1" x 1" (if possible) or (1" x 3" max as required)
I will do PCB Design from your schematic
I will do PCB Ordering
I will do PCB Assembling
I will do testing and provide you with assembled PCB for advance testing if you feel confortable with that.
I will do all Software Programming to interface Analog / Digital states to Spark Core MCU and build simple Web Interface.
I will do any and all aspects of project outside of design so you can concentrate on circuit functionality and improvement.
You will provide me with hand drawn or digitally made schematic showing components and in circuit design with values or value range for testing.
I will communicate with you in the manner you feel most comfortable. if out of the USA it should be done by Skype or a chat server. Your Choice.
Emailing docs and comments back and forth should also be a means of communication.
Would like to finish within 2 months time but, can be extended to make best design to minimize current used as this may be a battery operated circuit.
Attached files are examples of what I started and it does sense the Ring only.
10 freelancers are bidding on average $524 for this job
Hello..IM electrical electronics Engineer..I have experience project of microcontroller(PIC,MSP,ARDUMIOetc) programing and PCB desing..If you contact with me i want to do this work..I wait to hear you..