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Hypex DLCP/UcD400 build
Hypex DLCP/UcD400 build
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Old 13th May 2018, 03:32 PM   #1
ChrisHill is offline ChrisHill  United Kingdom
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Default Hypex DLCP/UcD400 build

I'm building a 6-channel integrated amp using a Hypex DLCP and 6x UcD400OEM modules. I posted a few questions in the Hypex DSP module(s) thread, but I've been feeling guilty about taking that thread off-topic by posting questions about interfacing to the UcD400OEM modules. So I thought I'd start a sort of build thread here, where I could ask some specific electronics questions.

I'm a novice at PCB designing, but since Hypex won't sell their OEM converter boards to non-OEMs, I've designed my own board. First samples are due in this week.

Click the image to open in full size.

I've attempted to make use of the 'clipping', 'current limiting' and 'amplifier ready' signals, by including LEDs on my adapter board to show their status. But now I'd like to think about putting 3 status LEDs on my front panel, and I'm looking for help with the circuit design.

What I'd like is for:
1) A front panel LED to light if *any* of the individual UcDs is clipping
2) A front panel LED to light if *any* of the individual UcDs is current limiting
3) A front panel LED to light *only* if *all* the individual UcDs is ready.

So I'll start with the current limiting (CLIM) circuit. The documentation for the UcD400OEM says that the current limiting signal is internally pulled up (limited to 5.6V I think), and goes low (to -VB, i.e. -63V) when current limiting. So on my adapter board I connected an LED between the CLIM pin and ground, so that when the signal goes to -63V I get current through the LED. What I want now is to take all 6 CLIM signals to a front panel PCB with an LED that lights if any of these signals goes low. Would somebody be able to take a look at the schematic below and tell me if I'm on the right lines?

Click the image to open in full size.

I would bring all the CLIM signals onto a 6-pin header JP1. LED1 to LED6 are the LEDs on my individual adapter boards. They are 10mA, 2V LEDs, so R1 to R6 are 6k1 - actually my board has two resistors in series for each of these resistors to give me flexibility over resistor values and power spec.

LED7 would be my front panel LED. D1 to D6 are diodes, because I think that if one pin goes low it would tend to pull all the others low as well, so the lights on each adapter would light. I'd rather that didn't happen, as I'd like to be able to look through the ventilation holes in the top of the enclosure to see which channel is current limiting. With those diodes I *think* I'd get only the LED on the corresponding adapter lighting up plus the one on the front panel.

Am I on the right lines? If so I think I can apply the same approach to the clipping signals (although they are the opposite way round: +63V normally, pulled to <=1V when clipping). The amplifier ready signals will take more effort I think, because I want a front panel LED that goes out if any of the amplifier ready lights goes out. Any suggestions for that one would be most welcome!

Last edited by ChrisHill; 13th May 2018 at 03:34 PM.
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Old 13th May 2018, 09:09 PM   #2
ChrisHill is offline ChrisHill  United Kingdom
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My electronics knowledge is really limited, and I can't work out how to get a single 'Amplifiers Ready' LED that lights when every one of the individual 'Amp Ready' pins is at -VB, but which goes out if any of the pins goes high.

Hypex provide this diagram to describe the Amplifier Ready interface.

Click the image to open in full size.

As far as I can tell, the transistor connects the Amp Ready pin to -VB via a 10k resistor when there's no error, but when there's an error it closes that path so that the Amp Ready pin is connected to +VB via a 1M resistor, but the voltage is limited to 5.6V by the zener diode.

So if 5 of my 6 amps are ok, but one has an error, then 5 are at -VB, via a combined resistance of 1/(5/10k) = 2k, and one is at +5.6V via a 1M resistor. So I think the 5 will win, i.e. one going high will not pull the others high - an LED controlled by tying these pins together would stay lit.

So I think some sort of logic is needed. My limited knowledge tells me that I could feed the front panel LED through 6 relays in series, each one switched by an individual one of the Amp Ready signals. So if one signal goes high the corresponding relay would open, so there'd be no circuit for the front panel LED. But 6 relays for one LED seems like overkill, and would be expensive. So there must be a better way.

I have a Raspberry Pi in the enclosure (acting as a Squeezebox server and player), and it possibly has 6 GPIO pins free, but I don't think I can monitor voltages of 63V.

So what about some sort of IC to handle the logic? Is there an easy way monitor the voltage of those 6 Amp Ready signals and only light my front panel LED when they're all at -VB?
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Old 14th May 2018, 01:16 AM   #3
rayma is offline rayma  United States
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Quote:
Originally Posted by ChrisHill View Post
Is there an easy way monitor the voltage of those 6 Amp Ready signals and only light my front panel LED when they're all at -VB?
You need a six input NOR gate, something like this.
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Old 14th May 2018, 05:55 AM   #4
ChrisHill is offline ChrisHill  United Kingdom
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Thank you, that's very helpful. I do appreciate your help, but my knowledge isn't good enough to take away a complete solution from that diagram.

Let me try to understand - are you suggesting I should use a 6-input NOR gate IC, and that diagram is simply an illustration of what the IC would do, or is that diagram something I could build from the discrete components shown, i.e. would I simply pass each 'amp ready' signal through a 10k resistor, then tie the outputs together as the base input to that transistor? Is 10k a value that you've selected to be suitable, given that each of my 'Amp Ready' signals will range from -63V ('ready') to +5.6V ('not ready')?

In the case of a single 'amp ready' signal going high to 5.6V, what would stop the other 5, at -63V, from pulling the tied output low?

Would I have to choose a transistor that can cope with -63V, or have those resistors brought the signals to acceptable levels?
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Old 14th May 2018, 10:36 PM   #5
ChrisHill is offline ChrisHill  United Kingdom
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My adapter board PCBs arrived today, earlier than expected. So I built one up with the components I've got so far - just waiting for the resistors to arrive now.

Click the image to open in full size.

What have I learned? A few things:
1) I need to leave more room around the mounting holes! The resistors will fit, but they're too cramped for comfort. And there isn't room for the jumper that I was going to install between the 'DC Error' signal and the on-board pull-up resistor (top-left). In fact I worked out that there's no reason to ever disconnect that pull-up resistor, so I soldered a permanent link between those pads on the underside of the board. For the next version of the board I'll remove that jumper altogether - I can always leave the resistor out if necessary.
2) Soldering things that connect directly to the ground plane is more of a challenge than other components. I deliberately didn't use 'thermals' for the high current connections, but the ground plane and those fat traces certainly make for good heatsinks.
3) It doesn't matter how much I try to think through of all the details, there's always something I didn't think about. I wasn't really expecting to get it right first time - I'm sure there'll be other problems when I power it up. It's a good job that each iteration is relatively cheap.

I've made the adapter so that the amplifier modules will sit vertically, with their backs to the sides of the enclosure, where there'll be some hefty heatsinks.

Click the image to open in full size.

I'm planning to use the Dissipante 3U enclosure from Modushop.biz.

Here's a mock-up of the current draft of the layout. The grid of crosses represents the optional baseplate for the Dissipante enclosure. The holes are at 10mm centres, so I've made all my boards with mounting holes to suit. The SMPS1200A400 has a mounting frame with holes that also suit the baseplate, but annoyingly the DLCP and SMPSDLCP have mounting holes that don't line up with the grid - I think I'll make separate mounting plates with holes that do align with the grid.

Click the image to open in full size.

Last edited by ChrisHill; 14th May 2018 at 10:43 PM.
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Old 16th May 2018, 03:55 PM   #6
rayma is offline rayma  United States
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Quote:
Originally Posted by ChrisHill View Post
In the case of a single 'amp ready' signal going high to 5.6V, what would stop
the other 5, at -63V, from pulling the tied output low?
Would I have to choose a transistor that can cope with -63V, or have those resistors
brought the signals to acceptable levels?
This is a NOR circuit. When any input(s) is (are) high, the transistor is on (collector is low).
Then the LED is off, because the 1k current is diverted from the LED by the transistor.

When all inputs are low, the transistor is off (collector is high), so the LED is supplied with
current through the 1k, and it lights up.

This circuit should work, except add a 1N4005 protection diode from the transistor base to ground
(cathode to base) to protect the BE junction from the negative input voltage. The 10k resistors
could be as large as 50k if you prefer.

Last edited by rayma; 16th May 2018 at 04:08 PM.
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Old 16th May 2018, 04:25 PM   #7
ChrisHill is offline ChrisHill  United Kingdom
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Thank you, that's what I hoped you'd say!

But I still don't understand 'how' the 'NOR' part functions. I understand that the transistor diverts the current when its base is high, but what I don't understand is why the base will be high in a situation where 5 of the tied inputs are at -63V and only one of the inputs is at +5.6V.

How does -63V + -63V + -63V + -63V + -63V + 5.6V = 'high'?

Can't that single +5.6V find a path to the other -63V pins, with the net effect that the 6 tied inputs all end up 'low'?

Click the image to open in full size.
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Old 16th May 2018, 04:41 PM   #8
rayma is offline rayma  United States
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Quote:
Originally Posted by ChrisHill View Post
I still don't understand 'how' the 'NOR' part functions.
Ok, this adds a clamp to ground for each input.
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Old 17th May 2018, 02:22 AM   #9
rayma is offline rayma  United States
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Quote:
Originally Posted by ChrisHill View Post
I still don't understand 'how' the 'NOR' part functions.

In fact, just do it this way.
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Old 17th May 2018, 08:43 AM   #10
ChrisHill is offline ChrisHill  United Kingdom
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Ah, now that one I can understand! Thank you, most appreciated.

In fact, I'm pretty sure that I've misinterpreted the way all three of these signals work (Amp Ready, Clipping and Current Limiting). I don't think they swing as low as -VB or as high as +VB - I think 'low' is at or near ground. So I think these pins aren't suitable to drive LEDs directly, but are intended only to switch an LED circuit, in a similar fashion to the circuit diagram you have kindly supplied. These LED circuits will need their own supply voltage, and I don't think +63V is the best place to start from, but that's the only voltage available on my adapter board. So I'm now planning to take these signals off-board to another board that will drive all of the LEDs, and I can use the auxiliary supply (+15.6V) on my SMPS to power the LEDs.

Your diagram has inspired me to do this properly with transistors. I have the option to have separate LEDs for each signal, so 6x Amp ready + 6x Clipping + 6x Current Limiting. Maybe I'll put those on the internal board, so I can take the lid off the enclosure and look at the status of each amplifier if I want to. But I'll also attempt to amalgamate these into 3 front panel LEDs:

- one showing when all 6 amplifiers are ready
- one showing if any of them is clipping
- and one showing if any of them is current limiting.

I'll use your diagram as a guide for how to do that.
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