TwoCubed Posted August 2, 2012 Report Share Posted August 2, 2012 Hi there! So I have finally gotten around to start building the first modules of the midibox sid v2. I have read a lot about the project and have gained much knowledge about it. I'd still consider me an absolute newbie when it comes to electronics despite having built some (more or less working) robot vehicle though. I have acquired the following LCD from Reichelt. It sports a white LED for the backlight. According to the datasheet, a white LED takes a supply voltage of 3.4-3.5v and a supply current of 20-25mA. Do I have to add a resistor at pin 15 or 16 of the LCD module or will the pot on the core module be able to regulate it? I'm just concerned because I measured much higher values coming from the corresponding pins on the core module. Should I need said resistor, my handy little smartphone app says I need a 75 Ohm. Is this correct? I searched the forum quite a bit before posting but I could only find similar problems related to the MB-6582 suggesting to add a 74k resistor in series somewhere on the core module itself. I'm building a modular mbsid though. I hope someone here can help me out because I really don't want to burn the lcd. Cheers! Quote Link to comment Share on other sites More sharing options...
ytsestef Posted August 2, 2012 Report Share Posted August 2, 2012 What PSU are you using? Maybe you're measuring excess voltage on the core module because it has no load? Try with a regular led with the same ratings as the lcd led. Normally no resistor is required. Quote Link to comment Share on other sites More sharing options...
Hawkeye Posted August 2, 2012 Report Share Posted August 2, 2012 (edited) The core module has the T1 (BC337) and a trimmer, which can be used to control the current flow through the backlight, so nothing too bad will probably happen. But ytsestefs idea of trying with a single LED is a good idea to test with a cheap part. Greets, Peter Edited August 2, 2012 by Hawkeye Quote Link to comment Share on other sites More sharing options...
TwoCubed Posted August 2, 2012 Author Report Share Posted August 2, 2012 (edited) Hey, thanks for the quick replies! I have indeed yet to build the modifications for the original c64 psu because Reichelt sent me the wrong caps for some reason. I will take new measurements as soon as that is done. I will probably try it first with the resistor and take it out when it's too dark. Oh and by "much higher values" I meant higher than the 3.4v. I measured 5v at 200something mA. Thanks for giving me a better feeling about this :) Edited August 2, 2012 by TwoCubed Quote Link to comment Share on other sites More sharing options...
technobreath Posted August 2, 2012 Report Share Posted August 2, 2012 Just to clarify - the resistor goes in series with the backlight - it's kinda obvious, but since u said u were a total noob on electronics, I guess there's no harm in saying it, no? :). Quote Link to comment Share on other sites More sharing options...
TwoCubed Posted August 2, 2012 Author Report Share Posted August 2, 2012 (edited) Haha, I totally appreciate the comment! But I actually figured that one out myself ;) Nice to point that out though because there was a time where I didn't know what the hell I was doing. That robot I was talking about, I killed it over and over because my soldering skills were complete crap back then and I didn't really know what the hell I was doing. I'm just glad I never really fried the µC. EDIT: I got the LCD up and running but I actually did have to add a 75 Ohm resistor. So I spliced open the ribbon cable and just soldered it in between. Works out nicely! (Don't mind the temporary cables everywhere, I'll sort that mess out soon :rolleyes: ) Edited August 5, 2012 by TwoCubed Quote Link to comment Share on other sites More sharing options...
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