Mezmerize DCB1 Building Thread - Page 12 - diyAudio
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Old 14th January 2011, 12:00 PM   #111
AndrewT is offline AndrewT  Scotland
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Hi,
The power feed to the selector relay comes from the same resistors that feed the mute relay.
If the regulator voltage is selected to match the relay voltage then these resistors are linked across (0r0). It will work fine.

If you use a higher voltage regulator than the relay is rated for, the resistors are used to drop the excess voltage.
If a second relay is brought "ON" it will drop the voltage applied to the "newly" selected relay even further and the newly selected relay might not trigger. The existing mute relay will not drop out due this voltage sag. There is a PCB mod that can overcome this (no details just yet)

This effectively means use 12V reg + 12V relays
or
use 5V reg + 5V relays.

I would stay with the 12V option for everything.

I love the idea of "press the selector button" and the LED confirms the selection. It would be even better if the selected button lit up, (a push to make button with a LED inside).

The LED could replace the emitter resistors R12 to R18, but then the supply voltage would need to be raised by ~2V to either 7V or 14V. This series LED would pass the same current as the relay coil. It will be very bright. Adding a resistor bypass across the LED will adjust the brightness.

If instead the LED is placed in parallel, then it must be in parallel with the relay. That involves 6 extra wires tapping into the PCB.
Neither way is brilliant, but both can be done.

Is there a third way?

Those emitter resistors are not required.
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Last edited by AndrewT; 14th January 2011 at 12:06 PM.
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Old 14th January 2011, 12:08 PM   #112
AndrewT is offline AndrewT  Scotland
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Default Mezmerize build

Put all your build tips, Q & A etc. here on assembling the Mezmerize version of the DCB1.
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Last edited by AndrewT; 14th January 2011 at 12:15 PM.
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Old 14th January 2011, 02:48 PM   #113
Bill_P is online now Bill_P  United States
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Are the switches mechanically ganged to keep from enabling more than one input at a time?
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Old 14th January 2011, 04:28 PM   #114
ramallo is offline ramallo  Europe
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Quote:
Originally Posted by Salas View Post
The way you use the chassis as a sink you can go 4x68R no problem. That will be about 120mA, but check the drop across the resistors for trimming current more equally between polarities. It usually differs. You can even go near 200mA and it will sink OK. ICCS=VRset/Rset.
I did a small hot rod

Click the image to open in full size.

Voltage drop across R= 1,57V and 1,53V.
R= 17,4 Ohm and 16,9 Ohm.
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Old 14th January 2011, 04:35 PM   #115
Salas is offline Salas  Greece
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Quote:
Originally Posted by ramallo View Post
I did a small hot rod

Click the image to open in full size.

Voltage drop across R= 1,57V and 1,53V.
R= 17,4 Ohm and 16,9 Ohm.
90mA per rail then. How is you output DC offset?
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Old 14th January 2011, 04:38 PM   #116
Salas is offline Salas  Greece
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Quote:
Originally Posted by nezbleu View Post
Hi:

Sorry if this is in the wrong place for this post, I can't find a thread dedicated to building the Mesmerize.
Here is such a thread. Merged.
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Old 14th January 2011, 04:55 PM   #117
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The spec of the Omron relays has a coil resistance of 1028 ohm, but can the resistance be less? The specified Omron relays aren't available in the UK, but there are others, including some with coil resistance of 720 ohms that I have the chance to buy at a good rate. Can I use these lower resistance relays?

Thanks
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Old 14th January 2011, 05:00 PM   #118
AndrewT is offline AndrewT  Scotland
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the coil resistance is not critical.

The pin layout must be identical, note that 2pins are not connected and thus do not need to exist on the replacement.

The contacts and the audio route through the relay should be similar for audio quality. I have no idea how you check that.

Only the mute relay and one other are active during operation.
12Vdc + 720r coil gives a current consumption of ~33mA, not a problem.
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Old 14th January 2011, 05:22 PM   #119
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Thanks for that - the realy spec says they're intended for Hi Fi and voice applications so we'll see if they're any good. Size and pin layout is the same as the Omron's.
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Old 14th January 2011, 07:37 PM   #120
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I've just started to measure some LED's based on the method of a 9V battery and a 1K resistor, but my Vf on the 1.8V leds I have is around 7.5 to 7.4V. If I deduct 7.4 from 9 that gives me 1.5V, but that's pretty poor compared to the marketed 1.8V.

And these LED's are the Mouser items referenced on the BOM.

Also, I've seen build thread pictures where they've measured 1.9V using the method above (9v battery and a 1K resistor), so how come I'm seeing approx 7V on my meter?

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