Note: This is an archive of my old Froglogger page. Some info may be out of date.
Most Sony portable MiniDisc recorders had two features that made them great for a Digital Audio Logger: a microphone input and a remote control. The remote control worked by closing a circuit between two of the four pins in the remote jack. I made some automated systems using an MSP430 microcontroller that triggered commands after a specific amount of time.
- Sony portable MD recorder (MD, NetMD, or HiMD; with mic input)
- Pelican case (model: 1120)
- Prototype Board for MSP430F1121 (model: MSP-P1121M)
- MSP-JTAG Parallel Port Dongle Programmer (model: MSP-JTAG)
- Hook-up cable (size 22-24), several colors
- Batteries cases
- Plastic enclosure for the controller
- Waterproof plug and jack (Digikey’s parts: SC1166-ND and SC1156-ND)
- Misc electronics parts (relays, transistors, resistors…)
How to control the MD recorder
The MD recorder receives commands from the wired remote control via a 4-pin connector next to the headphones jack (Fig. 1.) . You will need to use the remote cable, so just cut the remote cable ~6 in. from the plug. The cables to use will depend on the remote you are using. The recorder receives the commands from the second and fourth pins, counting from the headphones jack (see Fig. 1).
Find out which cables are in your cable and connect them in the circuit to the recorder as it appears in the diagram (Fig. 2). When the circuit between these cables is closed, the resistance value will tell the recorder what the command is. The specific resistance value differs between the older MD and NetMD recorders and the HiMD according to this table:
|Command||Resistance for HiMD (kOhm)||Resistance for NetMDand MZ series (kOhm)||Circuit in drawing|
|Pause (to start recording)||0.3||5.1||B|
Connecting all together
Using the MSP-P1121M board, you can connect the circuits to trigger the relays to the P1.0, P1.1, and P1.2 connectors on the board. These images may give you an idea of the process:
A tape recorder may last for a while in high humidity areas, but these recorders and microcontrollers are usually rated at lower than 85% humidity. Plus the expense makes it wise to use a protective waterproof case. I’ve used for MD recorders the Pelican 1120 case. It has space for the recorder, controller, and batteries. The microphone needs to be exposed to the air outside, so you can keep the contents of the Pelican dry using waterproof plugs. I’ve used pairs of SC1166-ND and SC1156-ND (available from Digikey) connectors. These have three gold-plated contacts and are waterproof. Just drill a hole on the side of the Pelican, secure the panel mount connector with the nut, use some silicone to seal the opening. In addition, seal with silicone the interior of the purge valve. This valve allows air to move to equalize the pressure in the box, but may also allow the entry of humidity.
Mounted on the side of the Pelican case: