apassgear said:
Currently, I am using 5v relays, as that is the voltage that the PIC, display and other control chips. It is obtained from a 9v 1A wallwart, and a LM-340T-5.0v regulator. The VFD draws about 500mA of current, or so it seems, but everything else doesn't draw much. Since none of the power is in the signal path, I didn't figure that it needed a better power supply. Am I wrong?
Here is the schematic for the pic board that I am using (page 6):
http://www.picbook.com/~pbpdf001/bookinfo/CA1.pdf
It is from a class here at georgia tech. More details at:
www.picbook.com You can actually purchase pcbs and a parts kit from digikey: 18F452-KIT-ND if you are interested in making your own pic development board. The whole thing could be obtained for about $120 including the book.
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Brian
BrianGT said:
I guess a simple PSU, as you suggest, would be enough. In my case I will do a "formal" small PSU to go in a separate box with the main power transformer for the active circuit of the preamp, and have the 5V IC regulator at the PIC board as I supose its provided. Haven't look to the layout yet.
apassgear said:
Not sure about this. I haven't given much thought to it. I am considering making a small power supply with one of those talema pcb mount toroids on it, on a seperate pcb for my power supply, and make it a regulated 5v. The vfd draws a lot of power, and worry about the long term reliability of the voltage regulator, as it is rated for 1A and it gets pretty damn hot, we had to upgrade the heatsink (originally had none). I am thinking about just making a 5v input to the passive volume control board, and then an input for the relay voltage, and if you are using 5v relays, just tie this the same. My roommate is doing almost all of the work for this project now, and I am trying to learn it as quick as I can so that I can help out with it.
What is a good plan for a regulated 5v power supply? It doesn't seem to be too important, as it only powers the control logic.
As for an earlier comment about the vfds making a lot of noise, if you look at the Passlabs amplifiers, all of the expensive ones have the vfd in the same chassis as the analog circuit, so it can't be that bad:
An externally hosted image should be here but it was not working when we last tested it.
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Brian
apassgear said:
It is the Pass Labs X1 preamp:
http://www.passlabs.com/prodlit/x1lit.htm
The power supply doesn't need to be overly complex, since it is jus for control logic.
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Brian
Brian,
It looks pretty interesting. I think I would be in for 2 or 4 channels if it didn’t happen too soon (too many irons in the fire right now). I know how you work though, it’s a glimmer in your eye one day, and the next day I’m looking at the finished product on your web site.
So I’m wondering what your expected time frame might be for putting an order together?
Rodd Yamashita
It looks pretty interesting. I think I would be in for 2 or 4 channels if it didn’t happen too soon (too many irons in the fire right now). I know how you work though, it’s a glimmer in your eye one day, and the next day I’m looking at the finished product on your web site.
So I’m wondering what your expected time frame might be for putting an order together?Rodd Yamashita
moses said:
I would guess that it is purely cost. From digikey, the cost is:
max232a: $5.51
max233a: $10.76
They appear to do the same thing. The only difference would be that you need 4 external caps for the 232a, and the caps are cheaper then buying the better chip...
Is there any other difference?
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Brian
roddyama said:Brian,
It looks pretty interesting. I think I would be in for 2 or 4 channels if it didn’t happen too soon (too many irons in the fire right now). I know how you work though, it’s a glimmer in your eye one day, and the next day I’m looking at the finished product on your web site.
Rodd Yamashita
It won't be too soon, at least a month until I get the boards done for my next prototype, then more time to order real boards for the order. If you haven't seen the current pics, there are a few more on the website:
http://brian.darg.net/relay
My roommate actually put this thing together mostly in 2 days (you really have to love those end of semester deadlines and college procrastination... I do it a lot myself) He was originally going to do the PGA2310 for it, but it just wasn't clean, and it wasn't working out the way that he wanted to. I showed him the P1.7 manual, and he decided that it would be much cleaner, and quite easy to implement. The hardest part was writing the remote control code, which initally had sync. issues. He is rewriting it now to make it a universal learning remote control receiver, so that you can use any remote for the volume control.
He spent much more time on his earlier project, which he finished on monday, his USB alarm clock:
http://brian.darg.net/USB-Alarm-Project
It came out really impressive, and worked great. It had bi-directional communication over usb, and you could set alarms on either the computer, or the microcontroller, and you could pick the mp3 that you wanted the computer to play when the alarm goes off. Look at the pics, I thought it worked out great. He asked me earlier if I could think of a way to implememt usb into the volume control
...I am slowly learning how to use the microcontroller, and am taking the class that he did next semester. The teacher put together a great book and board for the class, that anyone can buy and learn how to use fairly easily if you have basic programming knowledge. It has a C macroassembler, so you don't have to do straight assembly, although my roommate does anyway.
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Brian
I talked to my roommate some more about this project, and we have come up with a better plan for making this thing work:
-seperate boards for microcontroller and volume control board
-each volume control board is for 2 balanced channels. if you are not running balanced, simply only use one side of the relays.
-interfacing volume control boards with microcontroller with i2c, so that you can simply cable up to 16 volume control boards to this design, allowing you to have up to a 32 channel system.
-using the i2c addressing, the microcontroller can dynamically determine how many channels are present on the system, and they can all be configured seperately.
-each channel will have a label, and an individual setting (offset from master volume control)
-you will be able to change the balance of the board (mainly for 2 channel usage) and this will simply change the individual volume setting
-learning remote control receiver on the microcontroller board
-detailed menuing system for setup
-allow for user defined relay voltage, this would allow the user to pick whatever DPDT relays that fit the spacings provided (what spacings do relays have, are they standard?)
-microcontroller board pretty small
-volume control having short, clean signal path
That is it for now. We have the basic idea on paper how the board will be layed out. The microcontroller board will be quite small, and the relay board will be as small as possible, maintaining the shortest signal part possible (keeping it clean).
Mainly, this is intended to be a scalable design. Another possible advandage is that this might also allow for users to use other microcontroller boards, should you prefer to use an Atmel based board. The interface will be i2c, which is pretty common these days.
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Brian
-seperate boards for microcontroller and volume control board
-each volume control board is for 2 balanced channels. if you are not running balanced, simply only use one side of the relays.
-interfacing volume control boards with microcontroller with i2c, so that you can simply cable up to 16 volume control boards to this design, allowing you to have up to a 32 channel system.
-using the i2c addressing, the microcontroller can dynamically determine how many channels are present on the system, and they can all be configured seperately.
-each channel will have a label, and an individual setting (offset from master volume control)
-you will be able to change the balance of the board (mainly for 2 channel usage) and this will simply change the individual volume setting
-learning remote control receiver on the microcontroller board
-detailed menuing system for setup
-allow for user defined relay voltage, this would allow the user to pick whatever DPDT relays that fit the spacings provided (what spacings do relays have, are they standard?)
-microcontroller board pretty small
-volume control having short, clean signal path
That is it for now. We have the basic idea on paper how the board will be layed out. The microcontroller board will be quite small, and the relay board will be as small as possible, maintaining the shortest signal part possible (keeping it clean).
Mainly, this is intended to be a scalable design. Another possible advandage is that this might also allow for users to use other microcontroller boards, should you prefer to use an Atmel based board. The interface will be i2c, which is pretty common these days.
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Brian
BrianGT: No, just the lack of external caps I find is usually a blessing(and frees up a little bit of PCB space), perhaps you guys are a little bit more proficient with the soldering iron . The non-A parts are also cheaper, and just a tiny bit slower, which probably doesn't have much effect for the amount of data you're transfering back and forth.
. The non-A parts are also cheaper, and just a tiny bit slower, which probably doesn't have much effect for the amount of data you're transfering back and forth.
roddyama said:Brian,
How about extra outputs from the processor for relay selection of pre-amp inputs, or dual pre-amp outputs?
Rodd Yamashita
The microcontroller board will be capable of supporting this. Another board would have to be made, and if it is made using the i2c bus, it would be really easy to integrate this into the amplifier. It would just take running 4 control wires from the bus.
It doesn't really complicate things, but it would require making an extra pcb. The i2c chip for each board costs about $4 each in quantity, and one per expansion board is required. I don't know too much how i2c, but my roommate has a good grasp on how it all works (just finished two projects with it) and says that it simplifies the wiring a whole lot. each board would need vcc, ground and 2 control wires. It is a simple 2 wire serial bus developed by Phillips:
http://www.semiconductors.philips.com/buses/i2c/
This definately is not my first priority for this, but once the basic 2 board solution is worked out, this will be next on the list.
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Brian
moses said:BrianGT: No, just the lack of external caps I find is usually a blessing(and frees up a little bit of PCB space), perhaps you guys are a little bit more proficient with the soldering iron
Soldiering wasn't too bad for this. The volume control won't have this chip on it, since it won't be using the QuikBug (c) software. The chips will just be programmed with a programmer and put on the board.
As far as data transfers, it can take quite a bit to program this thing (1 minute) for large programs. It is quite a large pic. My roommate actually wishes that it went much faster.
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Brian
Attachments
csd said:
I am quite confused exactly what you mean by this. I can't seem to picture why you say that it is this way... can you elaborate a little more on this?
Another possibility might be using a table of values, and referencing that, and finding what values closely relate to the db scale, and scale it that way. A couple of relays could be added to the end to give 1024 total steps, then from this, a db scale could be determined as closely as possible, and put into a table. Is this possible through modifying the current configuration.
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Brian
roddyama said:Brian,
How about extra outputs from the processor for relay selection of pre-amp inputs, or dual pre-amp outputs?
Rodd Yamashita
Hell... since it is i2c, you could even run i2c temperature sensors from the processor board to each one of your monoblocks and monitor temperature from the display. I know that I am for mine. They don't cost that much either. There is a temperature on the development board, and I still like to use it to see what temperature my room is.
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Brian
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