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Tom.G
Science Advisor
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@Next_Of_Kintetic, for the reasons you just discussed, I recommend you stick with your original latching relay approach.
What the 3.3V pins? No, these are always at 3.3V. They provide power (up to 500 mA if I remember correctly) for attached circuitry e.g. this neat little real time clock module. You could use them to provide power to the relay board, but 3.3V relays are hard to find, you would be better off using the 5V pins: see below.Next_Of_Kintetic said:Although, couldn't I use those as well to send signals to the relay board that you linked?
Yes: don't turn it off (I would power the relay from the 5V pins (2 and 4) on the GPIO connector so this was not an issue - you don't need a separate wall wart at all). I think recovery from a power outage is going to be more complicated than just having the Pi remember which feeder is feeding.Next_Of_Kintetic said:That's kind of the point I was making though. Because then what happens if I switched to the "NO" position last time before I turned off the 3d printer. If I also turned off power to the relay (or let's say a surge happens, power gets cut off), then the relay reverts back to its NC state. When power comes back on, wouldn't it remain in the NC state unless something tells it to switch again?
No, the principal point of opto-isolation is to prevent you from being electrocuted. It (or some other physical separation) is a requirement in the UK (and I believe in the US) when switching line voltages from a device with low voltage connections (the wires to the Pi from the relay box if this is in a separate enclosure) or exposed metal (the USB connector on the Pi if this is in the same enclosure).Next_Of_Kintetic said:Wait, and this is probably my overall confusion about the subject, but I thought the point of opto-isolation is to protect high voltage surges from other parts of the system from wrecking circuitry that is not resistant to that high voltage.
No, the wall wart already includes protection from line voltages appearing on the output, the same goes for the printer and its control lines to the feeders. You only need to worry if you are switching line level voltages.Next_Of_Kintetic said:I mean, do I not have to worry about a high surge occurring within the relay from say the wall wart and then "cascading" back to the Pi?
A relay switch is an electrical component that uses an electromagnet to open and close a circuit. When a small current flows through the coil of the electromagnet, it creates a magnetic field that pulls a metal switch to make or break a connection. This allows the relay switch to control a larger current, such as the signals from a 4 pin connector, without directly coming into contact with it.
The purpose of using a relay switch to reroute multiple signals from a 4 pin connector is to control the flow of electricity and direct it to different components or devices. This can be useful in situations where multiple signals need to be sent to different places simultaneously, or when the signals need to be switched on and off quickly.
The right relay switch for your 4 pin connector will depend on the voltage and current requirements of your circuit. It is important to select a relay switch with a coil voltage and current rating that matches your circuit. You should also consider the number of contacts and their ratings, as well as the switching speed and type of connection (e.g. solder or screw terminals).
Yes, a relay switch can be used to reroute signals from a 4 pin connector in both directions. This is because the switch can be configured to either make or break the connection between the input and output terminals. By reversing the polarity of the current flowing through the coil, the switch can be toggled between these two states.
Yes, there are a few safety precautions that should be taken when using a relay switch. First, make sure to choose a relay switch with a suitable voltage and current rating for your circuit. Additionally, ensure that the switch is properly wired and secured to avoid any loose connections. It is also important to follow proper electrical safety protocols, such as turning off power before making any changes to the circuit.