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| Home > GCSE Projects > Two Way Intercom |
Modified:
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Designed by Phil Townshend, bulit by Tom Woodford 2005 |
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| CIRCUIT DESCRIPTION | |
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This circuit is a high gain amplifier designed to use the speaker as a microphone as well. Using 8 ohm speaker (66mm) the input is around 2mV. This is amplified by two transistor amplifiers and the low voltage TBA820M amplifier IC. The volume is controlled by VR1. A preset was used in this case but wires can be attached for a potentiometer if required. The master unit is usually set to receive and should be a DPDT push switch if possible. PB1 is a call switch, but you must press transmit also which will sound a tone of about 400Hz to the slave unit. |
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| The master unit houses the PCB, battery and speaker along with the DPDT transmit/receive switch. |
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The Slave unit just houses a speaker. The control over the direction of speech is accomplished by the Master unit. |
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| PCB AND COMPONENT DETAILS | |
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Below is the PCB layout. PDF format |
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Note these are to scale but not exact size.
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| PROJECT PICTURES | ||
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| A view of the Master enclosure. This was made by vacuum forming 2mm white polystyrene over a mould made from MDF and plasticine or modeling clay. It was then painted using enamel paints. The quality of detail achieved was excellent! |
The Slave enclosure was made in a similar way but not so big since it only has to house a speaker. Note the pattern of holes drilled for the speaker. | |
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