------------------- You don't say what relay you are using or what current it draws.
*** the relay should give something like "impulse" to the trigger electronics of ramp gate. So there is no current involved... The impulse will trigger ramp to open.
the base current will be 2,6mA instead of 2mA. If the raspbery PI port can handle and give this much or current then there is no problem. Nothing sho uld burn out ... OR am i missing something ?
Don't know about the rPi, but if any controller can't handle 3mA GPIO outpu t, there is something wrong with it. Most should handle 5mA. Some handle
20mA.
Yes, Python, Perl, Php, Java, C and C++. Why do you ask?
I have no idea what you are talking about here. In the schematic diagram you gave a link to there is a relay (K1) in the collector circuit of T1 bypassed by a diode. There are two types of relays in use. The first type is activated by a current being on or off. The other type is a "latching" relay which uses one current to set it and another current to reset it. This circuit is clearly using the former. So the relay coil must pass some minimum amount of current in order to guarantee the contacts are in the active state (pull in current). There is also a maximum current to guarantee the contact are in the inactive state called the drop out current. You can safely ignore the drop out current, but you need to make sure T1 is biased to provide the minimum pull in current. What is that value for your relay?
-- Rick
A typical 5V DC relay (8 pins in DIP 16 size) is around 20mA to 30mA to activate, less to hold. So, a 1K R(base), 3mA I(base) is plenty and is not too much either. Just use 1K and be done with it. We don't need to engineer this to death.
Yes, it shouldn't be under-engineered either. The OP asked a question about how much current the rPi output can handle. I suppose you would answer that the same way you responded to the question about the relay... *most* MCU outputs are fine with 2.6 mA. lol
Obviously the OP is new to this. Why teach him sloppy habits rather than teaching him to find the basic facts and figure it out for himself?
BTW, if the relay really is 20 to 30 mA, then there is no need to drive the base with 2.6 mA. With a minimum current gain of 100 just 0.3 mA is sufficient and 1 mA is more than enough. So a 2 to 3 kohm resistor is a better choice if you don't know the output drive spec on the I/O pin.
-- Rick
he's opening a door, typical magnetic locks are 2A at 12v or 1A at 24V
a DIP relay isn't goind to work well in that application for long,
but he hasn't said what's closing the door or how many times he wants to open it.
-- umop apisdn
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