# Reed switch (or other) for adafruit sound board

#### ThirtyWest

Joined Jul 15, 2017
140
Got my hands on an Adafruit Audio fx sound board (16mb).

It's got 11 trigger pins on it, and I'm using typical pushbuttons and such to activate some of the pins.

However, I'd like to find a reed swtich as i think that would do the trick; i want a simple switch that closes the circuit when the door opens (triggering a sound for halloween this year).

I found some $1 prox sensors at the dollar store which have a reed switch in them...normally off until you pull the magnet away. But, I'm wondering if I can cut the lines from the piezo buzzer and use them to connect the trigger's pin and ground on the adafruit board. Are there NO reed switches that use no power? I'm just looking to close a loop here. I'm still reading their forum looking for someone with that question already. http://www.robotshop.com/en/audio-f...8kOpD1SQD_IWu82fJCuqyqFNXxUrgRTRoCs9gQAvD_BwE #### MrChips Joined Oct 2, 2009 22,089 A NO (normally open) reed switch is simply a mechanical switch contact that closes when a magnet is brought up close. If the FX board already has internal pull-ups on the trigger inputs, all you have to do is connect the reed switch between the input and ground. No other external components are necessary. If you want to FX to trigger when the NO reed switch opens, connect the switch between the supply voltage and the input pin, Connect a pull-down resistor (try 1kΩ) across the input pin and GND. You could also use a micro-switch with a lever arm. These are usually available with three connections, NO-COM-NC. Hence you can wire it to suit the trigger requirements. #### philba Joined Aug 17, 2017 960 Have you gone to the adafruit page on the device? It has a ton of info. When asking your question here, it would help if you linked that to page. But in general, a switch is a switch. Your board will power it just fine. Don't use external power. The board schematic shows pull ups on the inputs. You can use security magnetic switches or even make you own contacts. Also, you'll need to make ogg files - it doesn't do mp3. Last edited: Thread Starter #### ThirtyWest Joined Jul 15, 2017 140 Have you gone to the adafruit page on the device? It has a ton of info. When asking your question here, it would help if you linked that to page. But in general, a switch is a switch. Your board will power it just fine. Don't use external power. The board schematic shows pull ups on the inputs. You can use security magnetic switches or even make you own contacts. Also, you'll need to make ogg files - it doesn't do mp3. It does ogg and wav--depending on your needs of response time (in ms) or file size. I'll look at the changeovers. I've inquired on their forums with no respones yet. This place here is fast for finding readers. I was thinking I could probably make my own with the proper magnet orientation and some coffee. Thread Starter #### ThirtyWest Joined Jul 15, 2017 140 Local store has free and cased reed switches. Adafruit says the pins are 5volt tolerant but to stick to 3.3v signals. Not a problem with reed switches, but there might be with a PIR. #### philba Joined Aug 17, 2017 960 The PIR is probably OK though you'll need to verify if it uses active low logic. Active high will probably be a problem with the onboard pullups. Thread Starter #### ThirtyWest Joined Jul 15, 2017 140 The PIR is probably OK though you'll need to verify if it uses active low logic. Active high will probably be a problem with the onboard pullups. They are slow to respond. Support. How would I find that out on the$15 harbor freight sensor?

The best I could do here is know the voltage passing out of it.

Come to think of it, I was needing to make a bridge rectifier and can't find the amp draw of the sound board

#### philba

Joined Aug 17, 2017
960
How would I find that out on the \$15 harbor freight sensor?

The best I could do here is know the voltage passing out of it.

Come to think of it, I was needing to make a bridge rectifier and can't find the amp draw of the sound board
When it doubt, measure it yourself. Which HF sensor are you talking about? I saw a motion activated security light and a wireless security alert system. Both will need hacking to use.

#### philba

Joined Aug 17, 2017
960
OK, a better way to do it, substitute a 4N35 or similar optoisolator for the led that comes on when it detects motion. then use the other side of the 4N35 as an active low input. If the circuit is not obvious to you, let me know and I'll draw it up for you.