airmailed Posted September 19, 2004 Report Share Posted September 19, 2004 I am interested in making a midi box incorporating light dependent resistors.. I am not sure which to use.. I would like to know which value (S) would be suitable to reproduce the effect of turning a pot or slider from closed to open...I have been looking at to the list at http://maplin.co.uk/search/menulevels.asp?CartID=040919191636321&Level=2&Criteria=&Menu=266&Exact=&Name=LDR%20s&Recs=&PrevMenu=16&PrevName=&LevelList= Does anybody know which ( if any) of these values would be suitable? best wishes..has anybody used these in a midi box already? Quote Link to comment Share on other sites More sharing options...
Duggle Posted September 20, 2004 Report Share Posted September 20, 2004 hithe simplest effective way to do this is to connect the LDR in series with a fixed resistor between 0 and 5V and connect the junction to AIN. (ie voltage divider).The value of the fixed resistor will determine the operating range. It may not be possible to produce output values close to 0 and 127 because the LDR will have a limited "light" minimum resistance and limited "dark" maximum resistance. Using more complicated circuitry it is possible to overcome this limitation but whether it is worth the design effort would depend on the application.cheers Quote Link to comment Share on other sites More sharing options...
airmailed Posted September 21, 2004 Author Report Share Posted September 21, 2004 thanks for replying, have you got any idea what value of LDR would be good to use? 9-20k?is it a matter of trial-and-error finding out which value of resistor to use in series? I thought of using a trim pot or pot instead of a resistor to add some element of controllability (to adjust for different light conditions etc) Any ideas which value to use? Best wishes Adam Quote Link to comment Share on other sites More sharing options...
Duggle Posted September 21, 2004 Report Share Posted September 21, 2004 hi,trial and error is a good idea, so only buy a couple of parts until you know the results are satisafactory.Without knowing what light source your using (I will asume natural light), the one with the lowest "light" resistance should be best (N59AY from your list).If you use R attached to 5V end and LDR to ground. Try 22k,47k,100k,220k some will give a lower minimum and some will give a higher maximum. Swap the LDR and R to reverse the response.A pot is not a good idea in that if it is in the "short" position you will get maximum current int the LDR and may destroy it.If you use a 10k resistor in series with 1M trim pot this should be ok though.cheers Quote Link to comment Share on other sites More sharing options...
msi Posted September 21, 2004 Report Share Posted September 21, 2004 You might try something like this.The potentiometer would allow you to control the voltage range of the VTL5C1. A resistor between the LDR and the VTL5C1 may be needed. I could be wrong but it seems to me that it would work. Quote Link to comment Share on other sites More sharing options...
airmailed Posted September 23, 2004 Author Report Share Posted September 23, 2004 thank you both for your replies..best wishesadam Quote Link to comment Share on other sites More sharing options...
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