Home Chapter 11 Digital sound memory, MIDI, reed relay
Digital sound memory, MIDI, reed relay

You can also add digital sound to your projects by using ISD Chips which are a bit expensive though for a lower fidelity and a quick method to add sound you can use Radio Shacks mini solid-state sound memory that stores up to 20 seconds of sound. Product number 276-1323.

Another option is to purchase a small MP3 player and hack into that. The nice think about hacking into an MP3 player is the sounds fidelity is quite good and the memory is solid state. 


20 second sound memory.


This product comes with a microphone and speaker built in, though you can use your computer to output sound and to download the sound into these solid-state sound memories from most sound editing software. You can also hack and activate MP3 players by using the relay below to activate play buttons or higher fidelity. 

You would have to 1) test the unit and see how it works 2) then remove the speaker and attach a sound jack compatible with your computer and wire into your computer 3) when you hit the record button on the digital sound memory unit also hit play on your computer and the sounds will be downloaded into the digital sound memory. (Careful to turn the record-out volume really low here) 4) Then unwire the jack or get a female to female jack that allows you to attach this sound memory to a pair of powered computer speakers. You will be surprised at how loud it can get and also that the fidelity is not too bad.

You can then attach the switch of the sound memory and use the BS2 or other microprocessor to activate the the sound. You can use a small relay like radioshack 5VDC/1A SPST Reed Relay to open and close the rewired activating switch. Compact 5VDC/1A SPST Reed Relay. Fast response, small size and low cost make this 5VDC relay a good choice for robotics, computer interfacing and projects that require several relays. Maximum switching power of 10 (watt/VA) Maximum switching voltage of 60 VDC, 120VAC Maximum switching current of 0.5 A Maximum initial contact resistance of 150m ohms


radioshack 5VDC/1A SPST #275-232


 These relays can also be used to switch on and off MP3 players that are wired to play a song continuously. This allows sound to be activated only when someone is in the room. What makes these small relays so convenient is they run directly off the microcontrollers output pins. 

Interfacing to MIDI

The MIDItron real-world interface is designed to simplify the process of creating sensor and robotics based electronic art projects.

The BS2 can also power midi outputs and this may achieved with the Basic Stamp, using the SEROUT command:

  1. Connect an output pin of the BS2 or PIC to pin 4 of the MIDI connector with a 220 ohm resistor
  2. Use another 220 ohm resistor to connect pin 5 of the MIDI connector to the +5V
  3. Connect pin 2 of the MIDI connector to ground


Wiring diagram for BS2.