Path: ...!Xl.tags.giganews.com!local-1.nntp.ord.giganews.com!nntp.supernews.com!news.supernews.com.POSTED!not-for-mail NNTP-Posting-Date: Thu, 30 May 2024 02:16:23 +0000 From: boB Newsgroups: sci.electronics.design Subject: Re: Optocoupler datasheets Date: Wed, 29 May 2024 19:16:22 -0700 Message-ID: References: <66574685$0$2363143$882e4bbb@reader.netnews.com> User-Agent: ForteAgent/8.00.32.1272 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 35 X-Trace: sv3-TWHxMZnaMOy3FvvEQdLaVnGu4dq27RiA9Z8TVdVDm2MO4rcFuKwAKLjWMpylMlR2tExtkZwp+5Amati!NItcSaln1lxyT8o1Pud45fHEbMgOEomuSljSIbkhKZ3VFxxpwgnYC7Z+P2AhM9IjP0Ac2IibZc2U!aqSBBL92 X-Complaints-To: www.supernews.com/docs/abuse.html X-DMCA-Complaints-To: www.supernews.com/docs/dmca.html X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.40 Bytes: 2525 On Wed, 29 May 2024 22:03:51 +0100, Clive Arthur wrote: >On 29/05/2024 16:15, bitrex wrote: >> Optocoupler datasheets seem like kind of a mess, I try not to use them >> too often in situations where there's any kind of power budget because >> other than "shove some relatively huge current through the LED like 5-10 >> mA" it's hard to know what you can get away with. >> >> A light load on the transistor side will definitely reduce the forward >> current required (and of course slow the speed to a crawl) but who can >> say by how much while still ensuring the thing will turn on sufficiently >> to saturate the output? >> >> The CTR varies widely from process variation, varies with temperature, >> varies with collector emitter voltage, varies with forward current, and >> the data sheets are full of caveats like "At I_f < 1 mA, note CTR >> variation may increase" and "Graphs are representative, not indicative >> of actual performance." ???? >> >> Any suggestions for how to approach methodically/mathematically >> selecting drive current would be appreciated, thank you! ("Don't bother" >> a valid option) > >Not really answering the question, but there's more than one way to skin >a cat... > >https://www.nve.com/Isolators You can also turn the LED off a bit faster and reduce off-time interference/noise by pulling the anode low, activiely. Not sure how much better it is though. boB