On 1/10/2020 5:04 AM, Mia Magnusson wrote: > Den Tue, 7 Jan 2020 11:58:04 -0600 skrev Jim Brain <brain_at_jbrain.com>: >> On 1/7/2020 4:24 AM, Mia Magnusson wrote: >>> Btw the level converters Raj Wurttemberg linked to will damage the >>> PI after a while if using more than one device on the IEC bus (in >>> addition to the PI), so for example combining a PI1541 with a real >>> 1541 should be done with the unidirectional active level converters >>> instead of those passive-ish bidirectional converters. >> How so? The FETs are open drain, so do not drive a high voltage at >> all, they just sink current. > Afaik all the sink current goes through the PI when using that > bidirectional converter. Therefore the slightly newer PI1541 hardware > with unidirectional level converters is the recommendation. > I didn't realize the Pi can't sink more than 16mA (max). That said, I'm not an expert on FET design, but I always thought the FET gave a "sink" assist, like an amplification, so the source need not sink so much current, but just enough to pull the FET into the sink "mode". Jim -- Jim Brain brain_at_jbrain.com www.jbrain.comReceived on 2020-05-30 00:15:55
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