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Re: Very simple Raspberry Pi Radio

Posted: Sun Mar 10, 2013 5:10 am
by gerben
I think they are referring to `jumpers` j1 and j2. Somewhere on the circuitboard the should be some connectors labeled J1 and J2 (and also J15 and J15). Probably on the backside, like in the following image ... 20Pic2.JPG

If all else fails you could try option 3 and connect the led directly. I thing the connectors are on the right of the lcd.

Re: Very simple Raspberry Pi Radio

Posted: Sun Mar 10, 2013 9:15 am
by Schwabinger
Thanks you very much for your fast reply :-)

Here is a macro foto of the LCD: ... hotostream

Yes, there is something like J1 or J2, but I have no idea on how to make use of those little dots ...

At the moment I connected PIN 15 and 16 to 5V/GND, but according to the document, it should be only 4.2.

I consider trying something like a voltage divider to get 4.2 out of 5V.

Re: Very simple Raspberry Pi Radio

Posted: Sun Mar 10, 2013 11:31 am
by gerben
The way I read it is; you only need the 4.2 when you are directly connecting the led (with the connectors on the side). Your way of connecting pin 15 and 16 would be option #2 from the documentation, which indicates it needs 5V
Does the led light up right now?! I can really tell by what you wrote.

But since the documentation is quite vague I would probably add a resistor between +5V and pin 15.

Forward voltage of the led is 4.2V; forward current 130mA. This would result in resistor with 6.8 Ohms needed. Which, I now see, is what the specification is saying.

No need for a voltage divider with leds, since they have a constant forward voltage. With leds you only need to limit current. I think that is the reason, but I'm still very new to this, and haven't fully grasped it yet.

Re: Very simple Raspberry Pi Radio

Posted: Mon Mar 11, 2013 11:39 am
by Schwabinger
Thanks for your fast reply!

The display is working but without any backlight (so you cannot use it in the dark).

Up to now I have tried the following - nothing worked:

Apply 4.1 or 4.3 to A and K; I did that by building a voltage divider and I only had resistors that resulted in 4.1 and 4.3 volts.

Apply 4.1 or 4.3 to pin 15 and 16; yes, you are right, the do not write that in the manual.

Apply 5 V to 15 and 16 without any resistor.

I hope I did´t break anything. I have no idea whether it is possible to only ruin the backlight and have the rest of the display working.

I still can apply 5V to 15 and 16 with a resistor with 5 or 6 ohms. But what do I have to do with J15 and J16?

Thanks again for your great help!

Re: Very simple Raspberry Pi Radio

Posted: Tue Mar 12, 2013 10:32 am
by gerben
The backlight is just an led, so you could break it, and have the rest of the display still work. But I don't think you have broken it. From the image it seems J15 and J16 already have something, I think it's a resistor across it. Also J1 and J2 have been shorted already. So I don't see how you could have broken it, without ever seeing it being lid. Driving this led with 5V without any current limiting resistor should break it immediately, just shorten it's lifetime.

I kind of suspect the unit already had a broken led.

The last think I would like you to try is connect the 5V and GND directly to the Anode and Kathode, so without any voltage divider, but with an resistor of 10ohms or more added to the 5V line.
Voltage dividers are only reliable for inputs (low current), not for driving an led.

I always forget whether the Anode goes to +5V of GND, so most of the time I just try both. As most LEDs have a greater reverse voltage than forward voltage, it can't damage the LED.

I that doesn't work I think the back-light is just kaput. You would have to return it, or live without the backlight.

Re: Very simple Raspberry Pi Radio

Posted: Wed Mar 13, 2013 10:32 am
by Schwabinger
I ordered a new unit of the same type yesterday.
We will see, whether it will work.

Re: Very simple Raspberry Pi Radio

Posted: Sun Mar 17, 2013 8:41 am
by Schwabinger
I built in a new lcd today.

This time I protected the backlight with a 10 Ohm resistor .... and now it works. ... otostream/

Next steps:

- Switching backlight on / off (need a transistor ... its on its way in the mail ...)
- Built in a pot in order to regulate the brightness of the backlight

@Gerben: Thank you so much for your support!

Re: Very simple Raspberry Pi Radio

Posted: Sun Mar 17, 2013 12:29 pm
by gerben
No problem. That's a nice looking LCD display, with the white on blue.

Today I added a LDR to my raspberry. I placed the LDR in front of the SPDIF output of my stereo. So now every time I turn on my stereo raspberry will start playing. And when I turn the stereo off, it will stop playing.
Once I get it to play my MP3 albums, it will resume playback from when I turned off the stereo, instead of keeping on playing.

Maybe you could use a LDR to change the backlight level based on the brightness of the room :-P
I'm just kidding.

Looks like we are both, slowly, getting our ideal sound setup.

Re: Very simple Raspberry Pi Radio

Posted: Tue Apr 02, 2013 7:46 am
by Schwabinger
Nice new feature for my RaspRadio:

I can now switch the backlight of my display on and off.

This is done by sending the line between backlight and GND through a transistor. Only if the transistor's GPIO is set to TRUE, backlight is on. Otherwise no blue light in the dark ....

Re: Very simple Raspberry Pi Radio

Posted: Wed Apr 03, 2013 1:59 am
by gerben

Now you can use sunwait and cron to automatically turn the lights on after sunset. :-P

Or only during playback.