USB-UIRT Forum

by **ElvisIncognito** » Mon Mar 10, 2003 6:58 pm

Hi, Jon.

I've waited a bit to post this, in the hopes that things may have slowed down a bit for you by now.

In this AVS thread: http://www.avsforum.com/avs-vb/showthre ... did=225197 there was a discussion regarding triggering power amps via the UIRT2. I think you & I discussed it briefly, but I can't remember the outcome. I do remember that it wasn't you (and was therefore probably Don Fukushima) that helped him with it, but I'm guessing that you would nevertheless know how to do this.

This is something I'm really interested in doing (with my USB-UIRT). I can hack the thing up a bit on my own if you wouldn't mind guiding me, or, if you'd rather not, I can send it back to you for a mod.[/url]

by **jrhees** » Mon Mar 10, 2003 8:00 pm

There are a few [semi]-unused i/o pins within the USB-UIRT which could provide an external trigger. A simple firmware modification could make these outputs available as well. The caveats are:

1) These outputs are useless when the PC is off (no USB power).
2) You would have to solder onto these outputs which can be a bit tricky.
3) Depending on what you're trying to drive, you'll likely have to put a transistor drive stage in to accomodate the required drive voltages.

-Jon

by **ElvisIncognito** » Fri Mar 14, 2003 5:24 pm

jrhees wrote:1) These outputs are useless when the PC is off (no USB power).

No problem. The goal here is to eliminate amplifier "turn-on thump" by powering up the amp - after the PC has booted - using Girder > USB-UIRT > internal relay built into amp.

jrhees wrote:2) You would have to solder onto these outputs which can be a bit tricky.

My soldering skills are reasonably good; I'm OK w/this.

jrhees wrote:3) Depending on what you're trying to drive, you'll likely have to put a transistor drive stage in to accomodate the required drive voltages.

That one's a bit scary. I'd much rather use a DC>DC converter (as mentioned in this thread: http://65.36.202.170/phpbb2/viewtopic.php?t=22 ). I know the amp wants to see 12V, but I'm not sure what the current requirements would be and/or if it's expecting a continuous or momentary signal. I'll check w/the amp manufacturer and let you know.

Thanks for the response & the help!

by **ElvisIncognito** » Mon Aug 04, 2003 5:35 pm

jrhees wrote:There are a few [semi]-unused i/o pins within the USB-UIRT which could provide an external trigger. A simple firmware modification could make these outputs available as well.

Hi, Jon. Sorry if this has already been asked & answered, but do recent firmware updates iinclude the necessary changes to make these outputs available?

I've had some discussions with the manufacturer of my amplifier (ATI) and here's what I've found out...

Per the THX spec, there's a DB25 connector on the back of my amp (and any THX certified amp) for remote turn-on. Pin 11 is positive and pin 23 is negative and they lead to a relay which expects to see 12V and at least 200 mA (and no more than 1A). This is not a latching relay, so the 12V 200 mA signal will need to be constant (and eventually removed to turn off the amp.) Is this a sufficiently low requirement to eliminate the requirement for a transistor drive stage?

Sorry for the delay in getting back to you on this (I've been busy), but now that all the data is in, I'd really like to move forward on this. Please consider posting a diagram on how to mod the USB-UIRT in order to make this signal available. If a transistor drive stage IS required, could you design one and give specific component values? I'm happy to be the guinea pig on this and work with you on an initial prototype mod to my USB-UIRT. Once I've successfully completed it, I can post a step-by-step procedure along with detailed photos for anyone else who wants to do this.

by **jrhees** » Mon Aug 04, 2003 6:12 pm

ElvisIncongnito,

Because of the amount of current required, AND the voltage of 12V, this will require BOTH a transistor output stage as well as an external power supply.

-Jon

by **ElvisIncognito** » Mon Aug 04, 2003 6:51 pm

That's fine, Jon. Seems like the logical thing is a simple, auxiliary circuit, external to the USB-UIRT (and possibly internal to the PC where 5V and 12V is plentiful) with a relay to be triggered/energized by a signal from one of these (currently unused output pins) from the USB-UIRT.

I can build such a circuit, but I need to know whether the USB-UIRT has the capability of controlling it.

And not just "if" but "how"... Can you give me a constant 5V at a reasonable amperage such that I can use it to energize a 5V coil on a relay whose contacts will pass the 12V to my amp's turn-on connector (and from there to its relay)? Or should I plan on powering the the coil as well as the contacts, using the USB-UIRT to simply make/break the coil circuit?

And what about the ability to programmatically control such a circuit (via Girder or ???) Are we there yet? If not, what are your plans for getting us there, and how soon do you think you could address this?

If we could achieve this, then we could also achieve power on from S4/hibernate/power off - I have no problem designing the circuit to accomplish this as well - I just need to know what sort of control interface you can supply...

by **jrhees** » Mon Aug 04, 2003 7:37 pm

ElvisIncognito wrote:If we could achieve this, then we could also achieve power on from S4/hibernate/power off - I have no problem designing the circuit to accomplish this as well - I just need to know what sort of control interface you can supply...

No..., not quite. To do this would require that the USB-UIRT remain powered when the PC is in S4 -- which is not the case for USB ports.

-Jon

by **ElvisIncognito** » Mon Aug 04, 2003 7:51 pm

Right. Makes sense. OK, then, we can skip that part, but I hope you'll still work with me on the amp turn-on issue.

by **ElvisIncognito** » Sat Aug 16, 2003 4:08 pm

I'd really like to proceed w/this, Jon...

I think the logical thing is a simple, auxiliary circuit, external to the USB-UIRT and internal to the PC (where 5V and 12V is plentiful) with a relay to be triggered/energized by the USB-UIRT.

I will design/build the circuit, but I need to know what I can get from the USB-UIRT to control it...

A constant 5V at a reasonable amperage (i.e. from one of those currently unused output pins on the USB-UIRT) would be perfect. I could use that to energize a 5V coil on a relay, and then the relay's contacts would pass the 12V to my amp's turn-on relay.

If you can't give me a constant 5V to energize a relay coil, (and I therefore need to power the coil as well as the contacts,) then I need to know what sort of trigger you CAN give me that I could use to make/break the coil circuit?

Could you also please address the question about the ability to programmatically control such a circuit via Girder? Are we there yet? If not, what are your plans for getting us there, and how soon do you think you could address this? And if not Girder, is there some other way that's either available now (or could be made available fairly easily and quickly?)

I think this is going to make a lot of people very happy - I really hope you'll work with me on this.

by **jrhees** » Sun Aug 17, 2003 4:38 am

OK,

To get you started on the circuit side of things, the simplest way to handle this is to find a small relay with 5V coil voltage with less that ~20mA coil current. This keeps you away from having to create a transistor drive stage just to drive a relay. There are plenty of reed-style relays which will do this -- if you need some more info on this, let me know. Heck, you can probably even find a relay at Radio Shack which will fit the bill -- yep, CAT #275-0232 will work just fine! You'll also need to add a diode in parallel with the relay's coil to protect the microcontroller's output pin.

As far as controlling a microcontroller output -- its simply a matter of re-enabling some features of the Girder plugin which have been disabled in the USB-UIRT plugin (that were available/created for the UIRT2)

-Jon

by **ElvisIncognito** » Sun Aug 17, 2003 6:00 am

jrhees wrote:To get you started on the circuit side of things, the simplest way to handle this is to find a small relay with 5V coil voltage with less that ~20mA coil current. This keeps you away from having to create a transistor drive stage just to drive a relay. There are plenty of reed-style relays which will do this -- if you need some more info on this, let me know. Heck, you can probably even find a relay at Radio Shack which will fit the bill -- yep, CAT #275-0232 will work just fine!

Jeez, Jon - I didn't ask you to design it FOR me...! :wink:

Thanks a bunch - 275-0232 should work very nicely - contacts are rated plenty high for what we need. Can the USB-UIRT supply a constant 5V @ 20mA or do I need to use a pair of these in a latching configuration?

jrhees wrote:As far as controlling a microcontroller output -- its simply a matter of re-enabling some features of the Girder plugin which have been disabled in the USB-UIRT plugin (that were available/created for the UIRT2)

That sounds like something that YOU need to do... ? Is this as simple as uncommenting a couple of lines of code and saying, "Try this version, Elvis - you should see 5V on pin X if you do this..."?

by **jrhees** » Sun Aug 17, 2003 4:03 pm

The USB-UIRT *should* be able to drive this relay OK without a latching configuration.

Once you get the relay and stuff, l'll post the details on where to connect it and send you a 'test' plugin.

-Jon

by **ElvisIncognito** » Mon Sep 01, 2003 9:03 pm

Jon-

I now have the relay, and I modified a 4-pin molex power adaptor to connect my 12V positive to the relay's contacts. I've grounded one side of the coil via the same connector.

Everything is now ready - awaiting your instructions and updated software.

by **jrhees** » Tue Sep 02, 2003 3:28 pm

Okay, here's what you need to do next:

1. First of all, REMOVE the ground from the relay coil. The coil will ultimately be connected between +5 and a pin on the USB-UIRT's microcontroller.

2. Make sure you have a diode ACROSS the coil connections. The diode MUST be present to prevent coil 'kickback'--which will destroy the microcontroller's output driver after just a few uses.

3. Connect one side of the relay coil (the same side which connects to the diode CATHODE) to +5V on the USB-UIRT. The best place to get this connection on the USB-UIRT board is where the RED USB-cable lead enters the USB-UIRT board.

4. Connect the other side of the relay coil (the side that connects to the diode ANODE) to PIN 3 of the USB-UIRT's microcontroller (this is the 18-pin SOIC).

-Jon

by **ElvisIncognito** » Wed Sep 03, 2003 12:01 am

So, it would appear that you're going to ground the coil for me instead of supplying it the +5V... so much the better. If that's the case, then why don't I just take the +5V from the same Molex connector that I'm using for +12V (as well as ground for the amp's turn-on relay)? That way, I'm not robbing the USB-UIRT of ANY voltage/current that would otherwise be available to it. Any reason not to do that? Or do we have some issues with the ground plane?

USB-UIRT Forum

Power amp trigger mod?

Power amp trigger mod?

OK - ready...

Something like this?

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