need a couple simple circuit diagrams

[Riot260]

#1: I ordered a set of switches for my integrated amp project and turns out they are momentary switches. They are nice and pretty so I'd like to keep them.

I'm drawing a blank.....I need a latching circuit with relay to convert to on/off switch. Any help greatly appreciated!

I could probably figure one out......... but a headache and an hour later are not in this weekends schedule.

#2: How can I step down 12VDC to 5VDC? I want to add bluetooth to my integrated amp project. I have 12VDC aux connections but the Bluetooth only needs 5VDC. Don't want to melt it.

I'm hoping someone could easily rattle one off the top of their head. Thanks

[Marvel]

#1 will be difficult. Once latched on, you would need to cut the power some way to cause your relays to 'unlatch'. It would be easier to spend the money to get the correct switches.

For #2, you can simply use a 5 volt voltage regulator.You can find the circuit easy enough online. It shold be something like a 7805 part number. Should be a piece of cake...

Attached is a data sheet for a Fairchild 7805. There are schematics towards the bottom. I assume you don't need much current. You may need to filter your 12 volts a bit more, but you can probably figure the rest out on your own. Parts count will be pretty low. You can get these from different manufacturers, and Radio Shack should even have some on hand.

You also might want to mount it on a heatsink.

Bruce

Fairchild_7805.pdf

Fairchild_7805.pdf

[Riot260]

Thanks. On the 7805: I am guessing the 4th unidentified terminal is all internally connected to GND. Input 1 is obviously going to be my 12VDC+ input. Output 2 is going to be the 5VDC+ supply to my Bluetooth module. GND 2 is going to be chassis ground? equipment ground? or 12VDC- ?

I will be able to mount this to the main amp heat sink, plenty of room there. Any mounting recommendations? I use heat conductive compound between amp & mounting plate. But I see teflon/ceramic insulation between the black plastic body and the heatsink, then a washer to transfer heat to the sink.

Or will it be fine simply screwed to the sink? If not who has the insulator?

Thanks again!

[Marvel]

Pin 1 is the input, Pin 2 is the GND (connected internally to the tab), Pin 3 is the output. Look at figure 8 on page 21. It's that simple. You should feed your bluetooth module from pin 2 (GND) and pin 3 (+5v). Don't forget the cap across 2 and 3.

You shouldn't need the insulator if your heatsink is already an electrical ground.

Bruce

[Riot260]

thanks might have missed the caps. looks like this will work great.