Brian

...and Multicomp (enclosure, switches, etc.) are not available via US suppliers.

That enclosure is available from a number of suppliers under their own brand. I haven't yet figured out if they are having their own extrusion struck or are buying from the master source here in the UK.

is that similar to what Canford would call KSM (BBC PSN20/4)?

Yes. I'm getting my PIN and PSN mixed up.

PIN is individual screened pairs.

PSN is overall screened pairs.

For any balanced line level stuff I'd usually use a basic FST (foil screened twin) or a multicore with similar properties.

Luxury! We used to use a lot of BBC style PIN for line level jackfields. For those not in the know that's multiple twisted pairs with an overall screen.

...pretty much any wall wart that comes to hand...

With the caveat that, because there is no regulation in our base station, if you end up with more than around 28v DC you run the risk of toasting your beltpacks.

You could send DTMF (telephone dialling tones) over the audio channel quite easily. There are 16 distinct tone-pairs so you theoretically drive 16 different tally channels.

The MV/MT8870 is a useful decoder.

re: Tally Signals

The problem would be that you need individual tallies for each camera so you know which camera is live. This means that, as a comms system is wired point-to-point and uses just a 3-core mic cable, there aren't enough wires running about the place to do this.

You could do a hack where you had multiple boards inside a box as your master station with separate cables out to each camera. Your tally feeds from the mixer, which are normally isolated relay outputs, would then wire across the call light button. This means you'd lose the ability to flash a call light on the beltpacks.

The other option would be to do something similar to the above but run individual 2-pair cables, maybe star quad, out to each camera, and use the 2nd pair to feed a tally light. The cable from the comms system would terminate in a 5-pin XLR mounted on the tally light which also has a 3-pin xlr output to feed the beltpack. This means that the comms side would be a standard system, all you'd need is an add-on tally interface and camera tally lights.

Excuse the quick drawing (done in papercad)...

The original PS-2 3-channel unit was 3 males.

The Eurolite single channel unit was a male and a female.

The Eurolite two channel rack mounted unit was two males and a female per channel

The Tecpro 711 3-channel unit is 3 males

The Tecpro 754 two-channel unit is a male and a female per channel.

VOLUNTEERS WANTED

Anyone interested in helping John and I get this finished?

What would be great would be some volunteers to take the parts list and each add one column to it containing a specific supplier's part numbers.

I'll post an excel spreadsheet here later tomorrow and if a few people could spend a couple of hours going through it and adding part numbers for the following suppliers it would be greatly appreciated.

Farnell

CPC

RS

Rapid

Maplin

We're quite keen to make this as universally available as possible hence the inclusion of Maplin.

And if there's any other online suppliers you think we ought to include then post here.

I'll look after merging them back in so if volunteers could each say which supplier they'll do.

We're looking at using the cheapest generic components we can find. The parts list ought to have enough info in it to identify what we need.

Thanks.

Belay that - the 8 pin dip is the one we want, isn't it?

It is. It's true that it's not the most common op-amp but it has a number of features which make it ideal for our application.

There is the L272 as an alternative but Farnell have that on EOL status although stocks are good.

I've attached a provisional parts list so people can see the sorts of things you need to build one. What does need adding to the list is information about things like lead pitch for capacitors.

The thinking behind the kit of hard to get bits is to keep shipping costs down. It's not good using a 71p op-amp if you have to buy it from the US and the supplier has an minimum order value of £30.

BluecomBeltpackPartsList_1_10.pdf

The PCBs are being designed to be manufacturable anywhere, any group buy PCBs are likely to be made in China. The finish of those is likely to be HASL (lead-free).

On lead-free solder, it's really not as bad as you might believe reading horror stories on-line. The solder itself is a lot better than it used to be.

I regularly use lead-free solder (from Rapid) and as long as your iron is hot enough (420C) it works just like lead-based stuff.

Thanks for the comments Dan.

We've discovered a few, mostly mechanical, errors on the first boards which means a version 2 will be needed for final checking.

I've bought parts to build a small system's worth of the v2 units so that we can test them together and know that they work properly. They'll also be tested in a system with other makes of pack.

One of the things we want to avoid is releasing something that doesn't really work.

Never soldered dual sided board from scratch before, only repairs. I guess there's a knack!

The board is 'plated through hole' so you don't really need to worry about 'the other side'. Just solder it up as normal.

As soon as we know...

a) that it works

b) that it fits the box

...we'll be releasing the files and thinking about a group buy.

This area is for projects which stand a good chance of going somewhere; it would be unusual for a project to start in here without the basic idea being kicked around in 'The Laboratory' first.

Only Project Leaders can start a topic in here although anyone is free to respond to an existing topic. This is done to keep things tidy, with all conversations relating to s specific project in the right place.

On creation the Project Leader will create a number of topics to a fixed format.

Topic Title: -> Project Name - Short Project Description

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Topic Description: -> See list below...

ANNOUNCE

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It is intended that all projects will be Open Source in the true spirit of that phrase. This does not mean people cannot have a commercial interest in the project, perhaps by offering a kit of parts or by charging for support, HOWEVER sufficient information must be published here to enable anyone to build the project without paying.

Looks like they're easily available as spares ...

They are.

I was simply going to point people at a few likely suppliers in the parts list. The fixing holes for the clip should be the only holes you need to drill and it's hard to get drilling two 3.2mm holes wrong (isn't it?).

I'm not sure how much vibration will come through a chunky metal case but, as boatman says, the circuit should drive one OK as long as you don't need too much current. Any motor current comes directly from the master PSU and eats into the number of slaves you can connect.

I suppose, as the pack metalwork floats wrt ground, we could always add an HV generator and fit a 'tingle' option for operator alert!

Just a quick reply to some of the points...

Even if you manage it the joint is fragile. Keeping the jacks is probably more reliable.

My thoughts entirely. Plus, the cable itself is usually quite thin and doesn't play nicely in XLRs. Ironically, sticking with the moulded 3.5mm plug will probably be more reliable.

could audio in and out be provided on unpopulated pads on the PCB so as to make the incorporation of the PCB into non-conventional applications easy, sort of a halfway to the AD903?

Probably. We'll look at squeezing a 0.1" pitch header onto the board. But see next reply as well.

It'd mean you could use the same pcb to make a master station with line in and out.

The AD903 has transformers in and out. Our output stage is already a high-current design which means it would quite happily drive a transformer. A change to a couple of resistor values in the mic amp would make it a line level input which could be fed from a transformer.

All this means it would be easy to make a version which has fully isolated 4-wire connections. This could be as simple as a little box, containing two transformer which plugged into a modified pack.

I've always been a fan of the "smart" Clearcom buttons with the double tap to latch, but I appreciate that this is probably outside the scope of this project...

IIRC Clearcom use a custom IC to do all the mic and call logic which runs off the Vbias supply (ie half DC volts) without any regulation, it is then capable of driving all the FETs etc without any level shifters.

How about doing the mic switching with a picogate D type or similar, so that a short interruption to the power from the master station can be used as master 'mic off' command from the prompt desk? I believe some of the Clearcom kit does something like this and it is usful when some muppet leaves a mic on and walks away.

See reply above about Clearcom. Doing it with 'conventional' parts will add quite a few components.

Also, some compression and/or noise gating? Possibly just a jfet across the mic line with fairly simple minded feedback?

We'll take a look. It depends a bit on board space.

Could we have an option to put a fixed resistor in line with the bottom of the volume control...

Don't see a problem with that.

...if the signal lamp control voltage were to be defined as ... I think this would probably be backward compatable.

I'm not sure it would be. As part of this project I've studied every comms pack I could get my hands on and they vary enormously in how they drive and receive the call lamp.

Does the design mean there's got to be a seperate connector if it's an electret mic?

No, the jack(s) are in parallel with the XLR. This gives the user the maximum options.

Thanks for the comments peeps...

What problems have you sorted?

1) We're providing a proper input for electret mics with gain adjustment at the mic amp to compensate for the different level.

2) The line drive section is different which should mean it works better on longer lines.

3) The hybrid section is revamped to improve sidetone rejection.

4) 2) and 3) together will improve stability.

5) By having everything on 1 PCB it will be much easier to build.

Did you get it working with cheap pc headsets in the end? There are some quite nice gaming ones for around the £30 mark that'll be nice disposable ones for schools work.

See 1) above. We're trying to track down a reliable source of 4-pole 3.5mm connectors to allow the use of both style of 'budget' headset.

Do I guess the power supply is just a supply with a terminating resistor?

Done properly it's 2 resistors and a capacitor to provide both DC and AC termination.

We'll put up some information on how it should be done.

Can I ask what's your power supply voltage?

It should work on all standard comms systems voltages which in reality means 24-36 volts.

In the past I've used PCBs as front panels with suitable holes, slots and screen printing. Mine had blue solder resist and white text. It's easy to design them on the same PCB package and they can be done on the same panel.

That's a possibility. We'll have a look.

I've updated the top post to reflect the fact that I'd forgotten about the electret mic option.

Question for you all...

For 'budget' headsets with electret mics and 3.5mm connectors, what is your preferred connector?

Announcing BlueClone: the Blue Room inspired comms system.

What is it?

It's an open-source industry standard live events comms system compatible with the bulk of wired comms systems used in the UK and beyond.

What is it not?

It is not a clone of any other similar project. We've gone back to basics and sorted out some of the problems that have plauged other systems.

I'm interested. What else do I need to know?

1) It's a single channel system.

2) All components, switches, pots and connector will be mounted on the single PCB.

3) It is being designed to fit into an extruded metal beltpack sized case.

4) The mic front end includes the option to provide the mic with a bias voltage to allow the use of electret mics.

5) The mic front end has selectable gain to allow the use of mics with higher output levels eg electret mics.

6) 3.5mm sockets are provided to allow the use of pre-wired headsets.

Who's behind it?

Myself and Boatman.

Where can I get the components?

We will be making the parts list available and basing the components around parts available from Farnell/RS/Rapid and CPC.

How much is it going to cost?

Our hope is that all parts, including PCB, box and metalwork would be around £60 incl VAT.

How difficult will it be to build?

You'll need to be able to solder 'standard' electronic components onto a PCB. As everything is PCB mounted there's no wiring to do.

What if it doesn't work once I've built it?

The design will be proven; we will have built working prototypes. Any problems will therefore be down to your soldering or a component issue. Support will be here on the Blue Room which, as you've spotted, is quite a helpful place.

Open Source? What's that mean?

It means that we will be making available all the information you need to go off and make you own comms packs. Specifically...

1) Schematics - we'll publish, as a PDF file, the complete schematics for the pack.

2) PCB - we'll publish the industry standard Gerber files you need to get PCBs made by your chosen supplier.

3) Metalwork - this design includes the full metalwork required to fit the PCB into our chosen enclosure and the required drawings will be released.

4) Parts List - we'll publish a parts list, listing where to get the parts you need, from UK suppliers and hopefully with at least two sources for each part.

I want to make my own PCBs from scratch.

Our PCB will be designed as double-sided with component pads and tracks that might not be suitable for home etching. However, it is an open source project so there is nothing to stop you taking our design and creating your own version, suitable for home etching, from it.

Are you using open-source software to design it?

No. We are using commercial software for both the schematic capture and PCB layout. Therefore it will not be possible for you to take our design and drop it directly into your own software.

Will you make design files for Eagle available?

No. See above.

I don't like the box you've chosen.

There's nothing to stop you taking our board design and mounting it into your own box by running wires out to the switches and connectors. Unless we forget them, we're going to put spare mounting holes in the corners.

I'm rubbish at metalwork. Everything I make looks like something the cat coughed up.

Don't worry. You have two options...

1) Take our drawings to your local sheet metal company and get them to make them or

2) Take part in a group buy (see below).

Will you be supplying any of the parts needed?

Yes. We will be doing a group buy on two of the non-standard parts...

1) We will be doing at least one batch of PCBs as a group buy.

2) We will also be doing a group buy on the end panels.

We would also encourage others, especially those based overseas, to organise a group buy for local BR members.

How will the group buy work?

1) We will announce a group buy along with the price for the part which will be the price you will pay, assuming enough people take part. We will give a closing date for the offer.

2) You contact us with a commitment to buy a specific number of parts. We will confirm your interest and at this point you will pay us via Paypal, the total amount owed.

3) Once the closing date is reached the order will be placed.

4) If because of the volume of parts ordered the price comes down, any excess will be donated to the Blue Room.

5) If we fail to get enough interest all monies paid will be refunded.

Doesn't this mean I have to trust you with my money?

Yes. Absolutely. However, enough BR members have met me to know that I'm far from an anonymous bloke on the 'net.

When will it be ready?

The electronic design is well advanced along with component selection. Some schematic capture and component library creation is complete. A 'will it fit' PCB layout has been done. Other work and holiday commitment's mean that not a lot will now happen for 10 days.

After that we will be getting a batch of prototype boards made. We're fairly confident these will work but wouldn't really want to offer these to people. Realistically, we're a month or more away from anything being available.

What's it going to look like?

Something like this...

How strong is that box?

Very. I've been using a larger version for stage pyro slaves for several years and they stand up to life on the road very well. You can quite happily stand on the one in the picture (I just have).

[edited 07/06/13]

Include details of electret mic option.

it has arrived with a piece of paper with chinese instructions and broken english translation explaining the DMX channels but no mention of gas

So, no clear instructions. Meaning its CE mark is invalid. Meaning that if you imported it directly you are about to break the law (and invalidate your insurance). Or if you bought it from an EU based organisation then they are breaking the law.

Apart from breaking the rules on CE marking you might want to look at what sections of the HSWA via PUWER has been broken.

There's a very good reason such units are cheap.

Could using non-snubber triacs in the past have damaged another part of the dimmer maybe?

Very unlikely. And if it did not in a way that would cause the problems you are seeing.

What is the PSC?

Prospective Shortcircuit Current

It's a figure, usually in the 1000A plus range, which indicates how much current your mains supply can deliver when it's short circuited.

If you're at the end of a long piece of cable the resistance of that cable will reduce the PSC. If you're right next door to a substation then it'll be higher.

If you have site electricians, or can arrange it next time an electrician is on site, it's a fairly easy measurement to take. Measured at the connection point for the dimmers it might give you an idea of what is going on.

Do you have these dimmers installed on any sites where they don't exhibit the problem?

Have you used the 610's?

 

...most of our venues use Betapacks ... I just dont understand why im having to put such massive triacs in these packs ...

I've not come across the 610s. I've used plenty of others including loads of betapacks without problems. It does seem very odd.

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