Path: ...!news.mixmin.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Clive Arthur Newsgroups: sci.electronics.design Subject: Re: Optocoupler datasheets Date: Wed, 29 May 2024 22:03:51 +0100 Organization: A noiseless patient Spider Lines: 29 Message-ID: References: <66574685$0$2363143$882e4bbb@reader.netnews.com> Reply-To: clive@nowaytoday.co.uk MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Wed, 29 May 2024 23:03:53 +0200 (CEST) Injection-Info: dont-email.me; posting-host="d05b00ceb6cf3bf29f87866f19aed732"; logging-data="1380270"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+KpJ0UwcHuEH4n2/aQDWPI4TGdhpA1I5I=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:S++zv2LTlHPKq60WDJKn3Ee/wRE= Content-Language: en-GB In-Reply-To: <66574685$0$2363143$882e4bbb@reader.netnews.com> Bytes: 2291 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 -- Cheers Clive