Forward baised photodiode
in [Design]
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From: Paul Hovnanian P.E. on 9 Jul 2010 21:13 Can you incorporate a current limiting resistor into the circuit? Even if the R degrades the ckt operation, put it together, verify that its at least the right way around and then swap the resistor for a jumper. -- Paul Hovnanian mailto:Paul(a)Hovnanian.com ------------------------------------------------------------------ Answer: Eight. Twelve if the light bulb is cross-threaded.
From: m II on 9 Jul 2010 21:49 Spehro Pefhany wrote: > Could they connect the PD backwards with the power supply already > turned on? There may be enough capacitance on the output side of the > current limiting to saut� la jonction toute de suite. > Nice going. Sneaking feminine French nouns into what used to be a polite thread. Who are you working for? Have you no shame? mike
From: George Herold on 9 Jul 2010 21:54 Spehro Pefhany wrote: > On Fri, 9 Jul 2010 13:10:21 -0700 (PDT), George Herold > <gherold(a)teachspin.com> wrote: > > >On Jul 9, 3:10�pm, Spehro Pefhany <speffS...(a)interlogDOTyou.knowwhat> > >wrote: > >> On Fri, 9 Jul 2010 10:26:57 -0700 (PDT), George Herold > >> > >> > >> > >> > >> > >> <gher...(a)teachspin.com> wrote: > >> >Right, who would do such a stupid thing? > >> > >> >This is for a piece of equipment that will be used by students. �They > >> >get to hook up the photodiode and it's guaranteed that 1/2 of them > >> >will do it backwards the first time. �(And the other half will do it > >> >backwards the second time.) �The power supply that biases the PD is > >> >current limited at about 250mA. �With this much current the forward > >> >drop across the PD (PIN-3CD from OSI) is 1.35 Volts at room temp. > >> >(0.34 Watts.) > >> >I�ve been cooking the PD on my bench for several hours. �It�s a bit > >> >warm, forward voltage drop is now 1.29 V. �(It�s nice that it goes > >> >down.) �From which I guesstimate the temperature rise to be about 30 > >> >C. �(60 mV) > >> > >> >Is this going to damage the photodiode in any way? � Seems like it > >> >should be fine. > >> > >> >Thanks > >> > >> >George H. > >> > >> Could they connect the PD backwards with the power supply already > >> turned on? There may be enough capacitance on the output side of the > >> current limiting to saut� la jonction toute de suite.- Hide quoted text - > >> > >> - Show quoted text - > > > >Yeah there is a switch and indicator LED, so hoepfully they turn > >things off before screwing around... But of course some will forget to > >turn it off. > > > >But I'll do a bit of live swtiching and see.... Well that might have > >cooked it. After several rapid forward biases something has changed. > >The forward voltage drop is now less than it was before...Hmm > > Glad to be of help. ;-) Yeah, If I put in a current limiting resistor and the PD still 'faults' because of hot switching, I'm not going to worry about it. Everyone has to make mistakes, a double mistake is a learning experience. George H.
From: George Herold on 9 Jul 2010 22:29 Paul Hovnanian P.E. wrote: > Can you incorporate a current limiting resistor into the circuit? > > Even if the R degrades the ckt operation, put it together, verify that > its at least the right way around and then swap the resistor for a > jumper. > > -- > Paul Hovnanian mailto:Paul(a)Hovnanian.com > ------------------------------------------------------------------ > Answer: Eight. Twelve if the light bulb is cross-threaded. Yeah, I think that may work. Have them hook it up first with a series resistor to check the polarity. I've got this floating terminal block that can be used. Thanks, George H.
From: Michael A. Terrell on 11 Jul 2010 02:25
GregS wrote: > > Once, I hooked up the Tripplet 630 to check out a large diode and it blew. > I could see the wire that fused. Was expensive too. > I just measured that meter to a ma. meter and was > about 200 ma at RX1. Have you read the manual for that meter? It, and others designed for troubleshooting tube electronics had a warning not to use it to measure resistance in solid state circuits. -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge. |