LED Soffitten mit 36V

[kfendt]

Hallo zusammen,

seit langer Zeit schon spielt mein B286 ohne Probleme meine Lieblingsradiosender - leider hat jetzt wieder mal der "Soffittenkiller" zugeschlagen - die Displaybeleuchtung mag nicht mehr.

Da nun mittlerweile LED Beleuchtungen auch in dieser Lampenform zu haben sind, würde mich interessieren, ob es irgendwo eine "kompatible" (Größe und Spannungsversorgung) LED-Lampe für meinen B286 gibt. Das Problem dürfte hier die 36V Spannung sein - im KFZ Zubehör habe ich bis jetzt nur maximal 24V (wohl für LKWs) gefunden. Irgendwelche Ideen?

Danke und viele Grüße aus München
Klaus

[blueTdi]

AW: LED Soffitten mit 36V

Ich habe da drei 12 Volt LEDs aus dem KFZ-Bereich in meinem B252 und auch im B261. War erst mal ein Behelf, aber funktioniert, allerdings noch nicht zufriedenstellend. Der Lichtstrom ist zu stark gebündelt, die Ausleuchtung ist nicht gleichmäßig. Bei Gelegenheit werde ich mal andere LEDs kaufen, die mehr streuen, und die dann mit entsprechenden Widerständen einbauen.

[steerpike]

Re: LED Soffitten mit 36V

Erlauben Sie mir bitte, auf englisch zu antworten...

I have recently changed the lamps in my B285 to 12x 3mm LEDs. Illimination is perfect. Perhaps you can find someone to make for you a suitable circuit board, as shown in my photograph.





The LEDS are arranged in groups of 4. So 3 resistors are required.
The B285 actually puts 19Vdc onto the lamps, not 36V. But the resistors can b adjusted for any voltage.

[blueTdi]

AW: LED Soffitten mit 36V

Very nice, that´s how it should be done.

Das kann man mit einer kleinen Platine schnell aufbauen, werde ich dann demnächst mal machen. Bei 12 LEDs muss man schon aufpassen, dass es nicht zu hell wird. Im meinem B252 sind übrigens nur 2 LED, also wohl 24 Volt. Muss ich mal irgendwann nachsehen.

[steerpike]

Re: AW: LED Soffitten mit 36V

Bei 12 LEDs muss man schon aufpassen, dass es nicht zu hell wird.

Indeed that can be a problem! However, I am operating the 12 LEDs at only 7mA. I have now photographed the display:

[kfendt]

AW: LED Soffitten mit 36V

Look beautiful indeed - is it possible so show a circuit diagram how the LEDs and resistors are connected? Which kind of LEDs did you use so the illumination is not too bright?

Addionally I'd like to get an external switching voltage to connect my active speakers and get them switched on and off using the B286 - do you think it is possible to add a connection (I am quite sure only a very low current can be measured there).

Thanks in advance
Klaus

[steerpike]

Re: LED Soffitten mit 36V

The circuit is as follows:





The LEDs I used are made by "Bright LED", 525nm green 3mm, BL-BG63V1V 4kmCd. At 4000mCd they can be very bright if required, but since I keep the current extremely low, they are not too bright. The Vfwd is 3.1V on this particular diode, which is unusually large for a green LED.

To compute the resistance for 4 series LEDs:
4 x 3.1v = 12.3v
Supply voltage (19v) - 12.3v = 6.7v
Desired current = 7mA: 6.7v / 0.007A = 957 Ohms
Closest standard resistor to 957 = 1kohm.

'Normal' Green LEDs need higher curent - maybe 15 to 20mA, and have a lower Vfwd of around 1.7 to 1.9v.

Both red wires to the lamp PCB in the B285 are the same - they both connect to +19v.

I would really like to make the LED brightness adapt with the ambient room brightness - as is done on the B250. But I cannot find a suitable location on the B285 front panel to position the light sensor photo transistor.

***

For a switching voltage: I assume the Microprocessor board is the same on the B286 as on the B285. The centre pin (6) of the 'serial' link socket is not used. This pin could be wired to the +16V switched supply rail (IC11, pin4).
Pin 1 of the serial link socket forms a ground. You could switch a relay with this voltage.

I'm not sure you can safely/reliably switch the active speaker direct with this voltage - i.e., omitting a relay, since you may create a ground-loop by connecting Pin 1 of the serial link (earth) to the speaker's earth.

And you'd need to be careful if you were to plug any other article into the serial link in future - check that Pin 6 is not used for any function in that article. (For example, on the B260, pin 6 carries RDS data)

[kfendt]

AW: LED Soffitten mit 36V

Hi steerpike,

thanks a lot for giving these very clear descriptions and instructions. I also found out that Pin 6 would be suitable for me and you also answered my not-asked question where to get the voltage from.

Within my B252 there is a similar modification done directly at ReVox: I also get 16,5 DC for the active speakers there which is taken from the processor circuit board; the advantage is that current is not active before the whole machine is powered up and I don't get any short peeks on the speaker control signal while connecting to power which makes the illumination sometimes flicker once.

I plan to add a relay and a fixed voltage controller delivering about 12V DC which is fine for my speakers; when switched off the relay grounds Pin 6 which makes the speakers going to Standby as desired.

Another question concerning illumination: Is there any blank or even populated "B28x lighting board" you'd probably like to sell?

Regards
Klaus

[steerpike]

Re: AW: LED Soffitten mit 36V

Within my B252 ... the advantage is that current is not active before the whole machine is powered up and I don't get any short peeks on the speaker control signal while connecting to power which makes the illumination sometimes flicker once.

I did not think about that - the brief pulse of voltage during AC power up.
An alternative then would be to take the remote voltage not from the +16,5V supply rail, but rather from the transistor for the relay which switches the B286 headphone outputs on/off. The downside here is that you have to link to the 'output amplifier board', it cannot be wired up on the processor board alone. Aditionally, the drive voltage to the relay is only +5V, and of low current.

I plan to add a relay and a fixed voltage controller delivering about 12V DC which is fine for my speakers; when switched off the relay grounds Pin 6 which makes the speakers going to Standby as desired.

Inside the 286 there is much free space to add your own inventions. You could add a simple delay circuit of your own, that waits 2 or 3 seconds before it switches on the new remote relay. This would require an additional transistor and capacitor.

The 285 is very crowded, no space for added features!

Another question concerning illumination: Is there any blank or even populated "B28x lighting board" you'd probably like to sell?

Unfortunately not. I made only one such board. Are there not electronics dealers in your town that will make a circuit board for you? I can supply you the artwork template if you wish.

[kfendt]

AW: Re: AW: LED Soffitten mit 36V

I can supply you the artwork template if you wish.

This would be very helpful indeed. I am sure that I will find somebody willing to create the circuit board for me.

In the meantime I googled for 4000 mcd LEDs you mentioned - you are using "clear" models, don't you? - it seems that these ones are not available here. Did you experience with LEDs brighter or not so bright than 4000 mcd? The only thing I found so far was a model from Nichia but this one is quite expensive. Are there suitable alternatives?

BTW: Did I discover special sockets for the LEDs on your picture?

Regards
Klaus

[steerpike]

Re: LED Soffitten mit 36V

I used those particular LEDs since they are the same ones I bought for my "Look-alike ReVox amplifier" drawing of B245 and I was impressed by the performance and colour, and I needed very bright ones for that project. They were not extremely expensive, €0.3 each. RS Electroniccs has very similar. It is quite shocking to see how much more you pay for electronic components over there. 4kmCd LED from RS Germany

This one is much cheaper, the 9000mC might be their mistake - i believe it should be quoted at 900mCd Cheaper RS 1000mcD

4000mCd is far too bright for the B285 at 15 or 20mA, so a lower Cd LED would be very acceptable; it would need more current than the 7mA I am using. I did experiment with a variable resistor to see how much light I needed, before I chose 7mA as most pleasing.

I did not use sockets for the LED, but plastic spacers for transistors, to lift the diode a short distance from the board transistor spacer pad.

Inside the green filter / mirror box of the B285 display, a placed a small strip of tracing paper (drafting film) to diffuse the light further.

I will put a link to the circuit board artwork later, once I have converted the file format.

[kfendt]

AW: LED Soffitten mit 36V

What do you think about these diffuse LEDs? Their dimension is 1400mcd

[steerpike]

Re: AW: LED Soffitten mit 36V

What do you think about these diffuse LEDs? Their dimension is 1400mcd

I think they will work OK: Since the B285/6 has a fresnel lens built into the display mirror, even diffused lighting will be directed onto the LCD. And 1k4mCd is still very bright - though they will possibly need more current than the 7mA I am using.

I have placed the artwork (pdf printable) here:
http://web.eject.co.za/s8nspawn/b285led.pdf

And the TangoPCB file here:
http://web.eject.co.za/s8nspawn/b285disp.pcb

Since the PDF file is large 2.3MB, I will only leave it there for a few days - I do not have unlimited server capacity.
If anybody wants to copy it to another server for long-term storage, they are free to do so.

[kfendt]

AW: LED Soffitten mit 36V

Is there any free software available which can read and probably adapt your TangoPCB file?

In the meantime I am thinking about a little extra circuit which is taking voltage from the illuminaton because I really do not want to touch the processor board (bad experiences within B252). Of course it's a little bit overkill but I'd like to use a NE555 IC for delayed power up speaker's remote control. After built up this little one I can experience with a few capacitors to get the delay I's like to have.

I think this could be a nice task for my first own circuit (of course I found an example in the web which meets my needs quite perfectly)

Regards
Klaus

[steerpike]

Re: AW: LED Soffitten mit 36V

Is there any free software available which can read and probably adapt your TangoPCB file?

Sorry, I do not know anything about capabilities of the various pcb layout packages. Any PCB manufacturer will be able to make a board from the printed paper image.
The layout is so simple that it would take not even 20 minutes to copy it using any pcb software, so converting the file is probaly more work than creating it anew.

In the meantime I am thinking about a little extra circuit which is taking voltage from the illuminaton because I really do not want to touch the processor board (bad experiences within B252).

Certainly you can do this. The display red wire is taken from the +16.5V, through two diodes, so it is approximately +15.5V relative to ground. The blue display wire is NOT ground, it is around -5v.

A 555, (or the low power version 7555) will be perfect for creating a delay.