Post by thread:[EE]: LED as a photodiode- theory! Please help wit

Hi again, Thank you for your replies to my question thus far. Advise me on the following by choosing the most correct answer. I think it is [2] or [3]. If I have two LEDs that are radiating each other from a distance of approx. 1mm and both are driven by current sources, then: 1. The diodes will become unstable 2. Electrical power to diodes will increase 3. Voltage across diodes will increase 4. Light output of both diodes will increase 5. Light output of both diodes will decrease Thanks. Regards, S. Sinha (Saurabh) Tel/Fax: (012) 343-4912 Cell: 0825405577 E.Mail: spam_OUTssinhaTakeThisOuTIEEE.ORG Visit: http://home.mweb.co.za/si/sinha [Home] Visit: http://ieee.up.ac.za/members/saurabhs [Work] [Underconstruction] WAP site (Access a small version of mysite thru' ur cell): http://mobile.worldonline.co.za ID:1011 [Underconstruction] ICQ: 82010326 {Original Message removed}

I haven't the time to give you an answer but I tell you what I will do for you . I will pass this posting onto my 12 year old nephew with a few components and some test equipment and see what answer he comes up with for you. I'm sure he will be able to come up with something over the weekend in between doing his homework from school. Chris Carr > Hi again, > > Thank you for your replies to my question thus far. Advise me on the > following by choosing the most correct answer. I think it is [2] or [3]. > > If I have two LEDs that are radiating each other from a distance of approx. {Quote hidden}> 1mm and both are driven by current sources, then: > 1. The diodes will become unstable > 2. Electrical power to diodes will increase > 3. Voltage across diodes will increase > 4. Light output of both diodes will increase > 5. Light output of both diodes will decrease > > Thanks. > > Regards, > > S. Sinha (Saurabh) > Tel/Fax: (012) 343-4912 > Cell: 0825405577 > E.Mail: .....ssinhaKILLspam@spam@IEEE.ORG > Visit: http://home.mweb.co.za/si/sinha [Home] > Visit: http://ieee.up.ac.za/members/saurabhs [Work] [Underconstruction] > WAP site (Access a small version of mysite thru' ur cell): > http://mobile.worldonline.co.za ID:1011 [Underconstruction] > ICQ: 82010326 > > {Original Message removed}

> Thank you for your replies to my question thus far. Advise me on the > following by choosing the most correct answer. I think it is [2] or [3]. > > If I have two LEDs that are radiating each other from a distance of approx. > 1mm and both are driven by current sources, then: > 1. The diodes will become unstable > 2. Electrical power to diodes will increase > 3. Voltage across diodes will increase > 4. Light output of both diodes will increase > 5. Light output of both diodes will decrease I admit that I don't actually know this answer, but I suspect that you won't see much of any measurable difference to a first approximation. Of course if you really want to know, don't ask, do it! I'd like to hear the answer when you find out. ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, olinKILLspamembedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

The only one I can be sure of is > 1. The diodes will become unstable and the answer is NO. Because the quantic efficiency is subunitary in both directions (emit and photovoltaic) there will not be enough gain for any instability to occur. I also think that you will need some fancy instruments to check this, because the efficiency of LEDs is very low (in both directions) and whatever change you will observe will be attenuated by this efficiency, squared. Peter -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam.....mitvma.mit.edu with SET PICList DIGEST in the body

Olin Lathrop wrote: > > > Thank you for your replies to my question thus far. Advise me on the > > following by choosing the most correct answer. I think it is [2] or [3]. > > > > If I have two LEDs that are radiating each other from a distance of > approx. > > 1mm and both are driven by current sources, then: > > 1. The diodes will become unstable > > 2. Electrical power to diodes will increase > > 3. Voltage across diodes will increase > > 4. Light output of both diodes will increase > > 5. Light output of both diodes will decrease > > I admit that I don't actually know this answer, but I suspect that you won't > see much of any measurable difference to a first approximation. Of course > if you really want to know, don't ask, do it! I'd like to hear the answer > when you find out. > from "circuits idea" Colin Pye ELECTRONIC WORLD may 2001 1 2 100k 2 0 22k 3 2 LED 2 0 100n 3 2 1M 3 2 1n 2 4 10k 4 5 1M 4 5 100n 3 4 7 0 5 TLo81 +in -in + - out with a short description of the behavior with various LED colours in photovoltaic mode. > ******************************************************************** > Olin Lathrop, embedded systems consultant in Littleton Massachusetts > (978) 742-9014, EraseMEolinspam_OUTTakeThisOuTembedinc.com, http://www.embedinc.com > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. -- Maurizio Viterbini Istituto di Fisica dell'Atmosfera Via Fosso del Cavaliere 100 00133 Roma Italy tel. +39 06 49934200 fax +39 06 20660291 email viterbinspam_OUTifa.rm.cnr.it -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics