Post by ryan on Apr 15, 2017 18:11:35 GMT
(This is not exocet-specific, so I'm posting in general, but do advise if there's a better location.)
After a couple of journeys at motorway speeds in the Exocet, it became clear that an intercom would be indispensable for both long journeys and at the track. I was not impressed by the value of the commercial options, so in the spirit of kit car building I decided to make my own. There was not much material online for this sort of project, but a few people had made intercoms based around LM386/LM380 amplifier chips, so my first attempt followed suit:
The result did work, but it had several shortcomings, so I decided to design a new circuit with all the features I wanted: robust and safe from electromagnetic interference, 150Hz-3kHz microphone filters to reduce wind/breathing noise, flexible auxiliary input and output (can be connected to smartphones, radios, recording devices), separate volume controls for driver/passenger intercom/aux, powered directly from 12V loom and highly customisable to work with different headsets.
The latest incarnation uses a small custom PCB inside a diecast aluminium enclosure from ebay, powered straight from a cigarette lighter socket. The blue leads run to the driver and passenger shoulder belts, and were put together using 4-core shielded cable, DIN plugs at the intercom end, and dual jack sockets at the user end. 3.5mm stereo sockets allow ordinary in-ear headphones to be used, alongside a 1/4" mono jack socket for the microphones. I made up some simple microphones using cheap electret mic capsules and 1/4" jack plugs, which are easily fed behind the cheek cushions of full face helmets. This system is more flexible and much more economical than proprietary headsets. I have several microphones made up, and guests simply use their own in-ear headphones.
The auxiliary input/output works wonderfully. When connected to a smartphone, driver and passenger can talk to each other, listen to music, and even take phone calls. (With the passenger operating the phone of course...) Next time we're at the track I plan to record a voice track to accompany the GoPro footage.
After a couple of journeys at motorway speeds in the Exocet, it became clear that an intercom would be indispensable for both long journeys and at the track. I was not impressed by the value of the commercial options, so in the spirit of kit car building I decided to make my own. There was not much material online for this sort of project, but a few people had made intercoms based around LM386/LM380 amplifier chips, so my first attempt followed suit:
The result did work, but it had several shortcomings, so I decided to design a new circuit with all the features I wanted: robust and safe from electromagnetic interference, 150Hz-3kHz microphone filters to reduce wind/breathing noise, flexible auxiliary input and output (can be connected to smartphones, radios, recording devices), separate volume controls for driver/passenger intercom/aux, powered directly from 12V loom and highly customisable to work with different headsets.
The latest incarnation uses a small custom PCB inside a diecast aluminium enclosure from ebay, powered straight from a cigarette lighter socket. The blue leads run to the driver and passenger shoulder belts, and were put together using 4-core shielded cable, DIN plugs at the intercom end, and dual jack sockets at the user end. 3.5mm stereo sockets allow ordinary in-ear headphones to be used, alongside a 1/4" mono jack socket for the microphones. I made up some simple microphones using cheap electret mic capsules and 1/4" jack plugs, which are easily fed behind the cheek cushions of full face helmets. This system is more flexible and much more economical than proprietary headsets. I have several microphones made up, and guests simply use their own in-ear headphones.
The auxiliary input/output works wonderfully. When connected to a smartphone, driver and passenger can talk to each other, listen to music, and even take phone calls. (With the passenger operating the phone of course...) Next time we're at the track I plan to record a voice track to accompany the GoPro footage.
