Hello to all and PM25 with Scanpro20's

[Carl B]

Hi Rob

Thanks for your diagram. Both the PM25 and the scanners will be used in differential mode. I know what you mean about which 2 end pins come together and go to ground but glad you pointed that out. If you are looking at a dual gang pot from the back the 2 pins on the right need to be connected together and taken to ground. This will make the pot increase voltage when turned clockwise.

As neather the PM25 or the scanners have actualy landed yet theirs not a lot I can do but I will keep you posted.

Carl

[Carl B]

Hi Rob

I was speaking to a freind last night about using duel gang pots on the signal input. He pointed out a problem with the tolerences of pots which can be as high as +-20% and this could cause an inbalence between the X+ and X- differential. He told me I'd be best to experiment with some fix 0.1% tolerence resistors of 5k and 10k and test them on a scope he can lend me. What do you think?

Carl

[stanwax]

Hi Carl

Yes standard Pots will have 20% tolerance - which could mean the signal will be attenuated unevenly. You would have to measure the pot to see how far out they were and if the difference was dramatic.
There are 2 alternatives...
A. you could just use 1% tolerance 10k resistors in place of the pot (as well as the first 10k - also 1% - in the branch) Take the output signal from the junction of the 2 this will half the input to the 5v you want. This will loose the ability to adjust on the fly - maybe good maybe bad.
B. Replace the fixed 10k with a trimmer (of more than 10k) to make adjustments in each leg to compensate for the Dual gang pot tolerance. More faff but accurate and still adjustable.

Bottom line however is the consideration of whether the 20% tolerance will make a difference that you will notice and that will depend on the individual components you buy. Remember 20% does not mean it WILL be out by 20% just it COULD be out by up to 20% - and like the shampoo advert that claims it will leave your hair up to 100% dandruff free that could be 1%.

Rob

[Carl B]

Hi Rob

I think using fixed resistors would be better as once I have set the signal level I don't intend changing it again. I've been looking through the Rapid Electronics catalogue and they do resistors with a 0.1% which should keep the signals in check.

I'll let you know how I get on when the PM25 and the Scanners arrive which should be this week.

Thanks Carl

[Carl B]

Hello People.

Just a quick update for this thread. I am still waiting for my PM25 from George. This is because of bigger issues he is having at work with a customer in Las Vagas.

One of my projector refits is nealy finnished and tested with my DMX system but I have decided to connect the scanner amps with single ended inputs from the desk as it's simpler to clip the voltage with trimmer pots. I'll see what the results are like and then decide if to revert to diferential input. Will post some pic's asap.

Carl

[Carl B]

Hello

I have finaly got a couple of photos done of both my refitted laser projectors. Got a couple of redundent holes to cover and to fit deviders and glass windows to prevent dirty air around the optics.

Attachment 2509
Attachment 2510

The two trimmers marked X and Y are to trim the 10v signal from the desk down to 5v to the scanner amps. These are fitted in both units. The Orange wire not yet connected in the second photo is to trigger a relay switch to flip the X axis in this unit witch will be controled from the desk.

Please feel free to make comments or forward any ideas.

Carl

[Carl B]

Just a quick up date regarding the refit to my two projectors.

As seen in the two last photos I have now got my new ScanPro 20 scanners fitted and working great even with single ended signals. I had also fitted the two CNI laser heads but after testing them with my TTL blanking DMX system I ended up having to remove them and refit my old TTL laser heads as the CNI ones with analogue blanking wern't happy with TTL blanking signal from the DMX board. Hope they work ok with the PM25.

Regarding the PM25, I still waiting for George at ChamTech to find time to finnish fitting the metalwork and to program the desk.

I've also got two empty enclosures coming from George as I've got a bit fed up of the heavy MDF one I built plus it's not very Pro looking. Below is a photo of the enclosures and one of the PM25 desk for those not familiar with one. I'll post some photos of inside the enclosures when they arrive. With these new cases this means i'll have to restart my refit from scratch again.

Attachment 2747
Attachment 2748

Carl

[stanwax]

Bloody hell Carl ya had me going then when I saw you had updated the thread I thought "hes got it!" The PM25 that is. Hope it comes soon - 2 months to the meet

Rob

[Carl B]

Hi Rob

You sound almost as excited about the arrivel of the PM25 as I am. I get the feeling your going to hijack it when I fetch it to UKLEM. I'm OK with that as long as your white setup is ready for me to play with.

What do you think of the enclosures. The dimentions are D : 310mm, W : 240mm, H : 150. The cases have a deviding plate with the laser and optics at the top and power and scanner amps in the bottom with the fan.

Sorry I got your hopes up about the PM25 and will reserve the next update of this thread for the arrivel of the desk and the enclosures.

Carl

[stanwax]

The enclosures look mighty fine - really professional - but then they should The partitioned bit is always a good thing. And yes I am really looking forward to seeing it in action and maybe even having a little play at the meet. As for my white - I gorra fix it first - but thats well and truly in the pipeline, will post news when some photons pop out the OC.

Rob