Any small electronics Gurus here?

[Jeff-Groves]

Need help on what should be a simple thing if I knew what I was looking for.
:doh:

I'd like ? in the image below to cut the circuit to the switch when the 3.3 to 5 volts power is on.
The pass through voltage for the switch would not exceeded 5 volts and is only used to ground the RX circuit.
The switch is a SPST Normally Open Momentary.

http://i108.photobucket.com/albums/n12/privateer_2006/Circuit-X.jpg~original

What this does (Or should do) is disable the switch circuit if the USB device is plugged in as that is where the 3.3 to 5 volts is drawn from.

And it needs to fit in here along with the switch.
http://i108.photobucket.com/albums/n12/privateer_2006/Playing.jpg~original

[Jeff-Groves]

The answer is, Anyone? Bueller? Bueller?

[vanjast]

The USB connector has a standard 5V supply connection.

That device looks like a USB to Serial (RS232) converter, and it looks like you have a choice of selecting 3.3V or 5V for the RS232 line supply.

As USB provides standard 5V, I'd imagine selecting that jumper, you'd bypass the 'buck converter' which would convert 5V - 3.3V

What are all the numbers on top of that 28 pin chip - the black thing with all the legs (pins)

[Wolferz]

Need more information.
What is that little box and what is it's purpose?
Standard memory stick?

If I had the numbers off that chip, I could possibly look it up.

[Jeff-Groves]

It's a USB to serial converter. The workings don't matter as I only need what I found out was a switching relay to cut the switch curcuit.

What this does is hooks my computer to the Shooting Chrony serial port.
I can download info then.
The Switch is called a Funcution Switch. It steps through options on the chrony when connected.
Problem is you can't use the FU switch when hooked in to the serial port.
Thus the FU name?
:haha:

Now imagine the new chrony I have that has the FU button next to the Forget button!!
FU and Forget!!
:har:
http://walterp99.siterubix.com/wp-content/uploads/2013/11/gamma-master-3.jpg

Now. Does the Timer button figure out when I hit FU and feed me the time till I hit Forget?
The Red ST button scares me! Not sure I want to know what it does!

[vanjast]

There must be a manual for this thing..
If you can find the manual download link.. I'll have a look, as one can easily work out technical details from just a user manual.

Also a manual on that USB device would be helpful..
:arrgh!:
BTW.. pull that jumper off the TXD/RXD connector and place it on the 5V/Centre pin. Just don't plug the USB device in yet until we've had a look at the user manual. :)
I'm currently going on the premise that your Chrony is 'old tech' which uses 5V.

[Jeff-Groves]

The jumper to RX and TX are a loopback for testing.
The Forget button does this.
https://s-media-cache-ec0.pinimg.com/originals/a9/70/ff/a970ff74b257fb5254f929ff01c57826.jpg

Now I don't remember what the FU button does.
:hmmm:

[vanjast]

That must be another movie :har:

Ok hang on.. I'll have to do a web search... but first I'm off to sleep
Later
:)

[Jeff-Groves]

The USB device is a Prolific. I have and know all the specs on it.
The curcuit to disable the momentary switch is all I need to know about.
It's a relay that will kill the momentary switch circuit IF I plug in the USB.
The 3 pins on the one side are the VDD voltage select.
The VDD is the 4th pin near the rear. No jumper on the 3 pins means no power to Vdd.
Don't need it for what I'm doing.

[Buddahaid]

Sounds like a job for a relay like this one.
http://www.digikey.com/product-search/en?KeyWords=255-1791-5-ND&WT.z_header=search_go

You can dl the datasheet and some circuit examples from the Digikey sight. I've used these and there needs to be a load resistor on the input side or they fry.

[Jeff-Groves]

Something like that seems right. As for a load? Could a 3.3v LED work?
That would show the USB has power when plugged in and the switch is dead.
The listing on the one linked says SPST-NO. I'll need to see if that's when powered.

Owww!! Now my head hurts!!!
:doh:
Trying to make something ID 10 T proof is hard!!

OK.
3.3v Blue LED with 320 ohm resistor should drop 5V down to about 1.6V?

[Buddahaid]

OK then maybe this one.
http://www.digikey.com/product-detail/en/AQW612EH/255-1979-ND/770460

I'm not sure just an LED will make enough load but an LED with a 100 or 200 ohm resistor would do it.

[Jeff-Groves]

DPST-NO/NC
I like that as I could do a dual button model.
:hmmm:

I don't have the specs on the LEDs I have as they are bits from an old computer case so I'm rough guessing the resistor.
I figured 320 or so and watch the LED and VOM.

[Jeff-Groves]

Here's how the serial stuff works.
The TXD RXD and Ground hook up to the Chrony with a 3.5mm stereo jack.

That same port uses a remote button that Grounds the TXD line which causes the chorny to step through readings that show on it's LED screen.

Grounding the TXD line while in Serial Control mode could damage things.
Thus why I want a way to keep that from happening.


I built a simple remote button. Gave it away.
I built several USB to Serial adapters. Gave them away.
Now I want to combine the 2 into one unit. So I can give them away.
I already have the USB to serial devices coming to put inside the chrony.
All the neat buttons are on the remote device anyway.

[Jeff-Groves]

Decided to go with this one
http://www.digikey.com/product-detail/en/CPC1125N/CLA385-ND/3508006

Way cheaper and should do fine. Even with a dual button this will work.