BlueClone - The Blue Room's Own Comms System

[dmxlights]

Hi Brian,

Thank you for your reply. I do have some built about a year or more. I will use some of these to do a test and let my friend know. I mite even get him to try and get me a tecpro pack and test it as well with mine on 12v.

 

[sunray]

Brian and I have rationalised the resistor values so that now 9 different values are used rather than 21 in version 1.3. I have also redone the PCB to change C22 from 100nF to 47uF. This is the de-bounce capacitor for the call button and some builders were finding the 100nF was far too small. 47uF should be adequate. It is possible to fit a 47uF capacitor in the C22 position on version 1.3 but the silk screen marking is less clear.

 

PLEASE NOTE that these changes are all untested but we would welcome a guineapig builder to test them for us.

 

The link to the zip file containing all the changes is HERE.

When I was sourcing/building packs I did wonder about the resistors used and assumed there was good reason for the fairly wide selection. I Will be building another couple but probably not for a month or two.

 

[Brian]

When I was sourcing/building packs I did wonder about the resistors used and assumed there was good reason for the fairly wide selection. I Will be building another couple but probably not for a month or two.

 

When John and I were kicking around ideas for this we spent a long while defining what we wanted this project to be. It was no good doing just another beltpack; we wanted to design the best beltpack. So we went and looked at as many beltpacks as we could get our hands on; I even scoured eBay and bought one of every type that I could. We also made a big list of the plus and minus points as reported by other people and highlighted a few issues around the system especially as regards the drive level for the common audio line.

 

Once we had our requirements list we set about designing our beltpack. And then testing it both as a standalone system and in conjunction with other brands of beltpack. And we ended up with what we think is quite a good design.

 

Since we designed it though, the component buying landscape has changed. Maplin has disappeared, minimum order amounts have changed, prices have gone up. It was time for a look again and see what, if any, simple tweaks we could make without compromising the original design.

 

And here we are with version 1.4.

[boatman]

When the original design was done 7 years ago there were many more sources of components and all the values were chosen for an optimal design. The resistor values have been rationalised down to only 9 different values from 21 to make sourcing the components easier. There are a few compromises in doing this which is why I emphasised that the design hasn't been tested, but should work OK.

[sunray]

I fully understand these comment from both of you and I know how easy it is to come up with a component during R&D and when it works it becomes the correct value without any further thought.

Having built [and modified] about a dozen of the belt packs with almost total success at initial power-up, other than C22 for which I am using a selection of values of about 5 to 25uF from the junk box following some posts a short while back it had not occurred to me that any values needed changing,.

The only problem I've had is the mic switch for which I have 2 issues:

 

The specified switch doesnt line up with the front panel hole, and

It's too close to the volume control and getting a finger between them for 'PTT' has been deemed too difficult, especially by anyone [follow spot operators] wearing gloves.

My solution has been to file a very small notch in the edge of the board to clear the metal part of the switch & mount the switch tipped slightly down, and inverted [so 'PTT' is towards the volume control]. I'm sure that doesn't make any sense without the bits in ones hands.

 

[boatman]

.

.

 

The specified switch doesnt line up with the front panel hole, and

It's too close to the volume control and getting a finger between them for 'PTT' has been deemed too difficult, especially by anyone [follow spot operators] wearing gloves.

My solution has been to file a very small notch in the edge of the board to clear the metal part of the switch & mount the switch tipped slightly down, and inverted [so 'PTT' is towards the volume control]. I'm sure that doesn't make any sense without the bits in ones hands.

 

I never had a problem with the switch lining up with the hole in the front panel. If you have any suggestions for a better PTT switch let me know and I easily make version 1.5 with a different footprint!

 

Of course it would mean prototyping a new front panel too.

[callumb]

Success! 5 packs and a PSU. Taken longer to get finished as I stupidly selected slow shipping from JLC on the front panel PCBs and need to pick up another case as I decided to make 5 packs instead of 4.

 

 

 

 

[boatman]

Looking good. Well done.

[andrew.p.r]

Evening,

 

A while ago I built up some V1.2 boards and the PSU not had a chance to use them in anger yet as have recently been in venues with systems already.

 

I was wondering though if it was possible to get a line level audio feed out of the beltpack board so I could hack one up to be show relay for one of our dressing rooms?

 

Thanks

 

Andty

[sunray]

I've used an isolating transformer on the headphone O/P.

 

 

If you are making a unit for the specific purpose components can be left out. If all you require is to inject the intercom into an amplifier for show relay, then all you need is an isolating transformer and a decoupling capacitor between ground and bus pins [1&3] of the intercom line loop and not a belt pack at all.

Evening,

 

A while ago I built up some V1.2 boards and the PSU not had a chance to use them in anger yet as have recently been in venues with systems already.

 

I was wondering though if it was possible to get a line level audio feed out of the beltpack board so I could hack one up to be show relay for one of our dressing rooms?

 

Thanks

 

Andty

 

I see you have no buttons yet. If they are still missing I have 6 available, they came from Mouser and over £1 each.

Success! 5 packs and a PSU. Taken longer to get finished as I stupidly selected slow shipping from JLC on the front panel PCBs and need to pick up another case as I decided to make 5 packs instead of 4.

 

 

 

 

Edited May 29, 2020 by sunray

[andrew.p.r]

I've used an isolating transformer on the headphone O/P.

 

 

If you are making a unit for the specific purpose components can be left out. If all you require is to inject the intercom into an amplifier for show relay, then all you need is an isolating transformer and a decoupling capacitor between ground and bus pins [1&3] of the intercom line loop and not a belt pack at all.

Evening,

 

A while ago I built up some V1.2 boards and the PSU not had a chance to use them in anger yet as have recently been in venues with systems already.

 

I was wondering though if it was possible to get a line level audio feed out of the beltpack board so I could hack one up to be show relay for one of our dressing rooms?

 

Thanks

 

Andy

 

 

That sounds perfect, Thanks for your help.

 

Andy

 

 

 

 

 

 

[Brian]

You will need to use a transformer, trying to take audio directly will not work. All comms systems run with unbalanced audio and introducing an additional earth to pick off audio from a belt pack will cause all sorts of problems.

[sunray]

You will need to use a transformer, trying to take audio directly will not work. All comms systems run with unbalanced audio and introducing an additional earth to pick off audio from a belt pack will cause all sorts of problems.

Oh yes all sorts of problems.

 

The big problem is the 'ground' at a belt pack is electrically so far from single earthpoint at the power supply/base station as the intercom circuit meanders around that making any other connexion to the ground at any point on the system is a massive no-no.

 

 

I have worked in a theatre where all of their tie lines screens were tied to electrical earth... total nightmare and completely unuseable for intercom.

 

[ChristoffSP]

Hi,

I did some searching through this topic and couldn't find a bill of materials for RS components or digikey, has anyone made one yet?.

I'll gladly compile one if it hasn't been made up yet and will also include any PCB alterations to allow the components to work.

Also want to check if anyone modified it to work with SMD components yet? Want to try and get it down as small as I can to use with camera's and also itching to use the new pick and place machine. Will also post progress on getting it smaller with SMD components.

[Brian]

Going SMD is certainly something you could look at. And after our recent tweak to resistor values it'll reduce the number of feeders on your P&P machine.

 

I think there are a couple of components that might cause an issue...

 

The FET is carefully chosen,not sure if it's available in SMD.

 

Ditto the opamp which drives the headphones. It was chosen because of its high output drive capability and its ability to tolerate shorts etc, an ordinary opamp won't cut it. But, if you went SMD it could be replaced with an ordinary opamp with an output stage beefed up with a couple of transistors. I have a design for such a thing that I've used over the years.

 

What P&P do you have? I'm always on the lookout for people who can do small production runs for my own work.