#robotics Logs

Feb 07 2019

06:28 AM SleepyTurtle1 is now known as SleepyTurtle
08:55 AM squirrel1 is now known as veverak
09:09 AM rue_mohr: -
10:10 AM veverak: hmm
10:10 AM veverak: rpi should be able to handle 3.3V gpio 'push low' relay ?
10:11 AM veverak: or, I have relay board are 3.3V and the pins has to be pushed low for the relay to turn on
10:39 AM polprog: youre not driving electromagnetic relays directly off gpio, are you
11:36 AM veverak: they have drivers
11:36 AM veverak: or I think so
11:36 AM veverak: anyway, I decided to fu it and inserted ULN2803 in place
01:00 PM polprog: good
01:31 PM mrdata_: veverak, digital output pins will be rated for a given source/sink current but relays are almost always greater than that so yes you do need a driver transistor
01:33 PM mrdata_: ULN series is easy like bread n butter
01:36 PM mrdata_: on a sunday morning
01:37 PM veverak: it's there
01:38 PM veverak: although I am sure that the relay board got custom tranzistors for the boards
01:43 PM mrdata_ is now known as mrdata-
01:47 PM mrdata-: compare source/sink current ratings
01:47 PM mrdata-: the relay board might even have opto isolators?
01:48 PM mrdata-: i have seen those on some boards
01:55 PM veverak: lately :)
01:56 PM veverak: yeah, it may
02:28 PM mrdata-: veverak, yes so even boards sometimes want like 100 mA source/sink but gpio pins might be 30 mA so in that case you might need a driver; but compare those ratings for your situation
02:38 PM deshipu: modern chips commonly have 8mA or less per pin
10:41 PM Tom_itx is now known as Tom_L
11:47 PM rue_mohr: no, the rpi cant drive loads