Pink noise generator circuit mod

[KrisBlueNZ]

I think we'll have to go the way I described. Here's an updated schematic. The extra components are RC (220R), DC (1N914) and RP (100K), and SW1 and K1.

SW1 is any SPST switch, i.e. a single set of contacts that closes when you want the noise to start up, and opens when you want the noise to stop, like that push-on, push-off pushbutton. If you have an illuminator, you'll need to connect it in series with the appropriate current limiting resistor (see earlier post) between +15V and the top end of the switch. I haven't shown that in the schematic.

K1 is a reed relay, but I've settled on 12mA coil types since they're more common. Three types are listed on the schematic. Here are links to them. They're all equally suitable. They are listed in order of increasing cost.

9007-12-00 http://www.digikey.com/product-detail/en/9007-12-00/306-1064-ND/301698
HE721A1200 http://www.digikey.com/product-detail/en/HE721A1200/HE102-ND/133189
HE3621A1200 http://www.digikey.com/product-detail/en/HE3621A1200/HE208-ND/133261
DIP12-1A72-12L http://www.digikey.com/product-detail/en/DIP12-1A72-12L/374-1234-ND/2765348

 

[culomax]

I suggest some changes to the circuit to include a switch that controls the charge and discharge of CT directly. It would also control the relay in series with the output signal. This would become the on-off switch and it would be the one you replace with a relay when you add radio control. The whole circuit, including the noise generator board, would be powered all the time while the speaker amplifier is powered.

Is that OK with you? Let me know and I'll post an updated schematic. The changes will not be large.

I had imagined that if I was to add RF control that this would be in series with the SPST switch rather than a replacement. Thinking about it now the other piece of kit we have with RF control allows you to override the RF control through the on/off switch. I never thought to look at the switch when I opened it up yesterday. It uses a HIRK-433A control module. 1 push powers the circuit on standby for RF control, 2 push overrides the RF control and starts the m/c. 3 push stops it. Hold down for 3 seconds to power off. I guess this is something you have to program into the module or is it some sort of 'smart' switch also.

To answer your question. I guess once the SPST switch is open the circuit will not be drawing current therefore the lifespan of the PNG will not be effected? Could we use a DPST switch instead. One-pole for the overall power to the circuit and the other pole to discharge CT. Could this be an option?

At this stage the circuit is getting a bit more complex so I might start with a breadboard rather than soldering the whole thing together. This will make tweaking it a bit easier. If it turns out good (which it will I might just buy a PCB etching kit and try make it neat.

Edit: Thanks for the updated schematic Kris. I will go order parts now.

 

[culomax]

Had a quick look inside the amp also. There is not much room on the control panel or behind it. The back of the control panel is sealed in a black plastic box.

 

[KrisBlueNZ]

I had imagined that if I was to add RF control that this would be in series with the SPST switch rather than a replacement.

That's OK. All you need is a single SPST contact of some kind, that's open when you don't want the noise, and closed when you do.

Thinking about it now the other piece of kit we have with RF control allows you to override the RF control through the on/off switch. I never thought to look at the switch when I opened it up yesterday. It uses a HIRK-433A control module. 1 push powers the circuit on standby for RF control, 2 push overrides the RF control and starts the m/c. 3 push stops it. Hold down for 3 seconds to power off. I guess this is something you have to program into the module or is it some sort of 'smart' switch also.

That's quite a versatile receiver module. It has three normally low logic-level outputs, which I guess have programmable behaviour? You could use one of these outputs to drive a transistor to perform the function of the switch contacts. That would be only a minor change.

To answer your question. I guess once the SPST switch is open the circuit will not be drawing current therefore the lifespan of the PNG will not be effected? Could we use a DPST switch instead. One-pole for the overall power to the circuit and the other pole to discharge CT. Could this be an option?

No, the whole circuit has to be powered at all times so that the DC voltage across the coupling capacitors stabilises. If you power the circuit up or down while the amp is connected, you'll get a thump. I wouldn't be worried about the lifespan of the noise generator circuit or the circuit you're making.

At this stage the circuit is getting a bit more complex so I might start with a breadboard rather than soldering the whole thing together. This will make tweaking it a bit easier. If it turns out good (which it will I might just buy a PCB etching kit and try make it neat.

That's an excellent idea!
You might consider buying a pack of assorted resistors as well. They'll come in handy one day!

Regarding space in the speaker enclosure, there are spaces round and between the speaker drivers aren't there? Shouldn't be hard to fit it in there somewhere.

 

[culomax]

there is plenty of space in the cabinet, Connecting into the control panel might be a bit tricky. Got a schematic back from the manufacturers that is no use as it doesnt show the component layout. Should be able to find suitable power rail with a multimeter.

 

[KrisBlueNZ]

You got a schematic? That's great! It doesn't matter that it doesn't show the PCB layout. The component references will all be marked on the PCB. Can you scan it and upload it somewhere, and post the URL here?

 

[culomax]

It's no good what they gave me but I'll post it anyhow.

I'm just ordering parts now but Digikey and other suppliers have no J310G JFET in stock. I've ordered this instead: JFET. Hopefully it is suitable?

 

[KrisBlueNZ]

The J310G is available from RS Components, not from Digikey. Are they not ex stock at RS Components either?

Digikey UK have three through-hole FETs ex stock - the J106 that you found, and the J111 and J112. The J112 looks like the best option - the J106's graph for gate-source voltage vs. drain-source resistance is not as smooth, which would make the audio ramp-up less smooth too.

The J310G will probably give the best result, as it has the smoothest graph. If you're getting your components from Digikey, you can try the J106 or J112 first, then get the J310G from RS Components if the ramp-up is too uneven.

I'd like to see that schematic too.

 

[culomax]

I checked RS earlier and it showed no results for the J310G. I've ordered the J106 from Digikey but can pop down to RS another type if needs be.

I should have ordered all from RS as I got the impression all the Digikey parts come from the US? They charged me £12 postage!

He are screen shots of the amp 'schematic' or thats what they have called it!

Page 1
Page 2

 

[KrisBlueNZ]

I checked RS earlier and it showed no results for the J310G. I've ordered the J106 from Digikey but can pop down to RS another type if needs be.

OK, we can try with the J106 and see how it goes.

I should have ordered all from RS as I got the impression all the Digikey parts come from the US? They charged me £12 postage!

When I buy stuff from them, it comes directly from America, but with the UK being a much bigger market than little old New Zealand, I thought perhaps they'd have stock there, too.

You could try Farnell, or whatever they're called now - Element 14, I think. They were originally UK-based, I think, so they may have stock there.

He are screen shots of the amp 'schematic' or thats what they have called it!

I see. That's not a schematic at all. I didn't think they would actually send you one. In a way, giving out a schematic is like giving away the source code to a commercial program. We'll have to figure it out ourselves.

 

[culomax]

While waiting for the components to arrive would it be worth looking at the RF control modules. I have had a look at a few different types but cant say I've figured them out. The main supplier in the UK seems to be RF Solutions. http://www.rfsolutions.co.uk/acatalog/RF_Development.html

I've been looking at various modules but I'm not sure what would be suitable for this application. From what I can gather is they mostly give an High and Lower Level output. The High level output seems to be 5V. Would this be sufficient V to control the JFET?

 

[KrisBlueNZ]

Yes, RF Solutions seems to be the answer.

The data-only products probably aren't suitable. All we need is a device that can produce a single logic-level output. Ideally it should be controlled so that one button on the transmitter turns the output on (high) and a different button turns if off (low), and ideally it should initially be low when the receiver powers up. That's all.

That output can drive a transistor or FET (N-channel enhancement MOSFET this time), that takes the place of the switch contact in the schematic.

It looks like their RDF1 receiver at http://www.rfsolutions.co.uk/acatalog/info_RDF1.html would be perfect except that I don't think you can program it so that one transmitter button turns a specific output on, and a different button turns the same output off. We might have to use two outputs, both configured as momentary, driving a flip-flop to remember the state.

The other alternative is having one button that toggles the output, but you don't get immediate feedback when starting the noise generator, so that's only practical if everything is 100% reliable, so you can be sure that when you've pushed the button, you can wait, and the sound will definitely start. If the system is not 100% reliable (e.g. RF reception is borderline, or the button activates twice when you push it), you might be sitting waiting for the sound to start when the control signal at the receiver is actually off.

 

[culomax]

The RDF1 that you linked to does look suitable. It appears that the each of the 4 Op's can be controlled separately depending on the transmitter used. This is what the datasheet says:

Digital Data Outputs
Each RF Solutions transmitter contains a secure serial identity. When a switch is pressed, the transmitter emits a unique secure RF signal. The Receiver can learn this signal and allocate it to any of its output(s).
Any transmitter switch may be paired to one or many of a receiver’s outputs,
Many transmitters switches may be paired to a single receiver output.
This enables
One transmitter switch to control many receivers outputs, or,
Many transmitters switches to control one receiver output

Like you said we would only need one OP's to control the circuit however I don't think they supply a single OP module. They have a tech support line so it may be worth giving them a call tomorrow to see what they would recommend.

One thing that does concern me is that if the transmitter gets lost/broken then its lights out! There are two solutions I can think of but not sure if it is possible without getting really complicated

1. When powered on the RF module OP automatically goes to High therefore the circuit boots up as normal.

2. As described in an earlier post, we have another piece of kit with RF control that uses this RF Solutions module: HIRK 433A (2008 so probably been replaced)
It allows user to turn on/off the m/c without the RF control using a momentary switch. First push powers on circuit in standby (can use RF control from here). Second push starts m/c. Third push stops m/c. Hold down switch for 3 secs to power off.

Ideally, if we could implement option 2 above that would be perfect. I will call RF Solutions tomorrow to see what they recommend. Maybe the modules can come pre-programmed with option 2 above. If you can think of anything I should ask them please let me know.

I also need to ask if a 17cm wire contained within the front grille of the speaker be a sufficient antenna.

 

[KrisBlueNZ]

Yeah, I read that part of the data sheet too, but I don't think it's saying that one button can turn an output on, and another button can turn the same output off. As you say, tech support can answer that question.

It might be better to email them; it gives them a chance to pass it on to the most appropriate person. You could also refer them to the data on your speaker, and ask them about antenna placement. Is the grille earthed? You should find out, and tell them that as well.

I don't understand your second suggestion for a backup control method. By all means ask RF Solutions about it. I would suggest a manual pushbutton, wired in parallel with the control from the RF receiver-decoder. You could use an illuminated button so it doubles as an indicator for when the speaker is in "noise mode".

 

[culomax]

Yes I see what you mean about the override manual switch in parallel. I had imagined a momentary switch in series with the RF receiver. I then thought that the switch would act like a controller through Pin 9. With the circuit been programmable I was thinking that momentarily adding 5V to Pin 9 would flip the state of the outputs (from Low to High or vice verse). I'm probably wrong but that's what I was thinking it could do.

I will need to call them to get an email address for tech support. Hopefully they can provide some direction.

The switch I ordered is illuminated so hopefully it can be put to good use but I dont mind if I have to get a mom switch instead.

 

[KrisBlueNZ]

Pin 9 is one of the VCC inputs to the receiver. Putting a switch there won't do anything useful. There is no input on the receiver that allows you to toggle an output; it's all just controlled from the transmitter.

If we use a flip-flop in between the receiver and the noise generator, so you can use two separate transmitter buttons, one for ON and one for OFF, it's not too hard to use a manual switch as an override to force the noise circuit either ON or OFF if the receiver is not generating output signals for some reason.

 

[culomax]

OK, that makes sense to me. I guess the circuit will always be powered when the amp is switched on but that shouldn't be a problem.

At this stage I think we will just just put the circuit into one of the speakers and link to the other speaker. I don't really see the advantage of having two separate circuits (apart from been wireless). I guess this shouldn't have any effect on our circuit as the amp will take care of the rest?

 

[KrisBlueNZ]

Right. I don't think it will be a problem having the circuit running all the time.

Sure, you can daisy-chain one speaker off the other. The input connector will double as an output connector when the noise generator is enabled. Does the amp have an unbalanced input? In other words, a jack socket? All I saw on the scans was a Cannon connector for balanced input.

 

[culomax]

It has a jack socket which says Input/Link. I guess we will be connecting into the jack input with our signal and then use an XLR to link to the other speaker?

Just thinking about it, we normally us standard audio leads but not sure it would work in this case.

 

[KrisBlueNZ]

For testing, you can wire the circuit to a jack plug and plug it into the jack socket on one speaker.

Once you mount the circuit inside a speaker, it will be soldered to the jack socket inside the speaker, and you can use a jack-to-jack cable from that jack to the jack socket on the second speaker.

The XLRs will be connected to differential-input preamps so no noise signal will come out of them.