Adding LED's to indicate switch state

[downtownpaulyp]

John, I notice all MSA versions use the same circuit board. Very clever design!

I'd like to add LED's to indicate the open/closed state of each switch.

Do you see any issue with connecting LED's with appropriate limiting resistors from the top of R0 - R7 to ground to do this?

As long as R0 - R7 are properly installed as pictured, (vertically over the indicated circle in each location) it would be a very useful mod that should work for any version of MSA.

You might also consider adding this as a future feature. I bet it'd be a huge hit!

[GoatBoy]

:) I was planning to pop my MSA-R in a box and connect leds with resistors directly to the outputs as well as the solenoids I'm operating to do the same thing as an indicator that the circuit's working to that point! Can that be done also?:confused: I'm a little ham fisted with these things!

[John]

John, I notice all MSA versions use the same circuit board. Very clever design!

I'd like to add LED's to indicate the open/closed state of each switch.

Do you see any issue with connecting LED's with appropriate limiting resistors from the top of R0 - R7 to ground to do this?

As long as R0 - R7 are properly installed as pictured, (vertically over the indicated circle in each location) it would be a very useful mod that should work for any version of MSA.

You might also consider adding this as a future feature. I bet it'd be a huge hit!

Your idea will work fine. A couple of points:

The resistors R0-R7 connect the microcontroller (IC1) to the corresponding relay K0-K7. For the MSA-R, these resistors are 0-ohm, so you can connect the indicator LED circuit to either side of the resistor.

However, for the MSA-P & MSA-T, you must connect the indicator LED circuit directly to the output from IC1, before it passes thru the resistor R0-R7. (otherwise, the indicator LED will "compete" for current with the output relay/transistor, and the output may not operate correctly).

Also, keep in mind that any LEDs that you add may increase the MSA current consumption beyond what is specified in the hardware user manual.

Finally, limit the current thru any of your indicator LEDs to 10mA or less--this will prevent overloading of the IC1 output pin.

The circuit will look like this:

[R0]----|>|--\/\/\/----[GND]

...repeat for R0-R7.

Hope this helps...thanks for the suggestion. If the MSA hardware is revised, indicator LEDs will likely be added.

[John]

:) I was planning to pop my MSA-R in a box and connect leds with resistors directly to the outputs as well as the solenoids I'm operating to do the same thing as an indicator that the circuit's working to that point! Can that be done also?:confused: I'm a little ham fisted with these things!

You could also do it this way. Personally, I would lean toward the setup described in the previous post--it would make things easier if you ever need to make changes to your solenoid circuitry (different power supply, etc).

[downtownpaulyp]

For the MSA-T and MSA-P, installing the resistors "backwards," with the body of the resistor NOT over the circled pad would make for an accessible connection at the top of each in the proper place--before the resistor.

I'll get mine all together and let you know how it comes out!

[downtownpaulyp]

John,

I am happy to report that tying in to R0-R7 for LED status indicators works like a charm! I've installed green 5mm (T 1-3/4) LED's at 9mA or so using 510 ohm limiting resistors.
I'm using a 500mA 12VDC supply just to be safe.

To keep a harmonious look, I also used these same LED's for power and activity indicators.

The only issue I ran into so far was a tiny solder bridge that was fouling up the voltage divider for controlling my Mesa Boogie Nomad amplifier.
That's what I get for soldering into the wee hours of the morning.

I have 6 LED's remaining to install tonight, then full function testing. I'll try to post some video of it all in action.

Thanks again for an awesome product!

[downtownpaulyp]

As promised, pictures of my project using an MSA-R, adding LED's from R0-R7 to indicate relay status.

All Lit Up
The two rows of 4 LED's indicate relay status.
Far right LED is power, second from the right is MIDI activity.

http://forum.highlyliquid.com/attachment.php?attachmentid=4&stc=1&d=1234992470

Rear Panel
Bottom left is power.
5-pin DIN is for MIDI in.
7-pin DIN is a custom jack for relays 1-4 to control channel, solo, and reverb functions on my Mesa Boogie Nomad amplifier.

http://forum.highlyliquid.com/attachment.php?attachmentid=5&stc=1&d=1234992470


Relays 1 & 2 are internally wired to voltage divider resistor networks for channel switching on the custom amp jack.

Relays 3 & 4 are also internally wired to the custom jack, but are basic short-to-pin.

Relays 5-8 are completely isolated.

Because I used switching jacks, custom functions on relays 1-4 are bypassed when plugging cables in--similar to muting speakers on a stereo when headphones are plugged in. This allows future functionality if I ever change amplifiers, or alternatives to amp functions if I desire.

Project case is a Hammond with mounting wings, which I will use to attach to a rack shelf in my guitar rig.

[John]

As promised, pictures of my project using an MSA-R, adding LED's from R0-R7 to indicate relay status.


Nice work! Thanks for posting the photos. What's the model # of the enclosure?

[downtownpaulyp]

Case is a Hammond 1591 series with a flange kit. I bought it locally with the flange kit installed for about $11.
It happened to be a good size for a 1/2 width rack project, and not too tall, with enough room to get all the jacks mounted.

PC boards are mounted on 1/2" nylon spacers using #4 screws, there's just enough room to squeeze it all in!

Lemme know if you want to see any internal pics. It's quite a maze of wiring in there.

[teKILLa]

Case is a Hammond 1591 series with a flange kit. I bought it locally with the flange kit installed for about $11.
It happened to be a good size for a 1/2 width rack project, and not too tall, with enough room to get all the jacks mounted.

PC boards are mounted on 1/2" nylon spacers using #4 screws, there's just enough room to squeeze it all in!

Lemme know if you want to see any internal pics. It's quite a maze of wiring in there.

Please post some internal pics, I'd like to see where LEDs are connected.
Could you also specify the type of LEDs?

[Achben]

Why not just employ a jumper/terminal-block instead of the 0 Ohm resitors? Heck, do you know of such a device that would already fit the PCB?

[John]

Hi Achben,

Yes, for the MSA-R, in order to "tap" into the relay coil signal, pin headers with 0.1" pitch could be attached to the board instead of the 0-ohm resistors. Of course the signal would still have to be connected across the pins for the relays to work.

I'd recommend a "breakaway" style header, since the resistor holes are arranged such that header lengths of 6, 6, and 4 positions could be used. (or 8 separate 2-position headers.)

Not sure if I answered your question or not...