Phone Isolation - Analog / Digital outputs

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.

Evner: Digital Design, Elektronik, Microcontroller, PCB Layout

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Om arbejdsgiveren:
( 0 bedømmelser ) United States

Projekt ID: #6042536

10 freelancers are bidding on average $524 for this job


Hi, this is an interesting project, many, many years ago I used to be a telephone engineer, so I know a little about phones although this was with ring dialling. I would have thought that a simple current transformer Flere

$555 USD in 10 dage
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Dear Sir, We are Reserach and Development company whose working area are : -Digital Motor Control -Analog Design -Electronic Design -Power Electronics -PCB design -Embedded system -Matlab -Simulation of ha Flere

$555 USD in 20 dage
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Detector call can be done using an optocoupler. Measure current too optocoupler (it adds 1.2V drop in the line - which is insignificant).

$400 USD in 15 dage
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Hello, Let me introduce myself I am yasir amir khan. I am electrical engineer, running an online consultancy business, with several years of project related experience. Please check out my profile. and search my name o Flere

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$750 USD in 10 dage
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hello, i am an electronics engineer and an embedded system designer with expertise in both analog and digital design. i also have good PCB design skills. i am qualified to work on this project. looking forward for you Flere

$650 USD in 15 dage
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Electronic Engineer and expert with Analog /digital circuit design (I have done similar kind of experiment as telephone operated switch panel) (visit my profile for more details ) Thank you Chamika Gamage Ele Flere

$555 USD in 10 dage
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HI I am a design engineer and i am having a professional background on designing custom made solutions for various products. Further I can deliver you the best solution for your problem as I have followed my BSc in el Flere

$394 USD in 30 dage
(2 bedømmelser)

i have worked on such projects before i can help you with this one. please contact me for more details

$300 USD in 20 dage
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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..

$500 USD in 12 dage
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please check our company freelancer profile we already developed this type of project so we can take your project. why you hire us ? have 5*** with 100% complete rate with we Flere

$350 USD in 8 dage
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Hello, I am an embedded systems designer and developer and would love to work on this project because am designing telephone interfacing circuits for the last 15+ years. Kindly contact for further conversation an Flere

$555 USD in 10 dage
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