I'd like to make a button which sets / resets latching relay through arduino, which means that after power outage the relay keeps the position. For example if the LED bulb is powered on and power outage occurs, the relay keeps the position. After power comes on, the LED bulb is powered automatically as the relay haven't changed the position. I have found this relay:
Is this relay fits my requirements? This relay is SPST-NO, but I can't understand why does that matter on latching relays (why does it matter if its NO or NC) because I can change relay state and leave it until I want to change the state again? Also, can I even send signals from Arduino directly to this relay, or I should choose 5V relay instead of 12V?
JCA34F:
What is the LED bulb's voltage? How much current (Amps)? Why would you need NC contacts? Link to relay does not work.
Spreadsheet:
The LED bulb was just an example. I will use relays for water pump, fuel pump and so on (under 10A limit, 12V). For example I want to turn water pump for 24 hours - the regular relay would use some current and it wouldn't be efficient. So, to answer your question - to switch on/off some of the accessories.
when you start with + on the correct pin. And you have a DT relay, you have a COMM and both a NO and a NC
when you have a ST relay, you still have a COMM, but then have to just pick something to call the other pin.
since OPEN is normal, it becomes NO. and there is no NC.
but, you are correct in your questioning why call it anything except contacts ?
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you are required to have some sort of a driver circuit to power this relay.
low power coil is 0.4 watts. with 5v that is about 80mA. too much for a pin of an Arduino
Remembering things is what the EEPROM is for. The only limitation is how many times you may re-write it - in the order of tens of thousands (or more). So unless you propose to to press your button(s) ten thousand times during the lifetime of the system, that will not be a problem.
The only difference is that I would use 12V supply instead of 5V as shown in the image. Is this diagram would still be suitable for 12V? Or I should change some connections?
No eeprom
Latching relay uses a magnet to hold contacts closed.
Requires a pulse to revert back to the natural or normal state.
Hence the high power and low power pulses.
Normally is the unlatched state.
You can make a points switcher circuit
Resistor cap to store the charge needed to switch. Used for model trains.
dave-in-nj:
No eeprom
Latching relay uses a magnet to hold contacts closed.
Requires a pulse to revert back to the natural or normal state.
Hence the high power and low power pulses.
Normally is the unlatched state.
You can make a points switcher circuit
Resistor cap to store the charge needed to switch. Used for model trains.
I prefer to use 12V as power source for switching, as I'm using car battery as the main source to power up Arduino (12V to USB) and all other appliances. I have made this circuit:
Arnelis:
I'd like to make a button which sets / resets latching relay through arduino, which means that after power outage the relay keeps the position. For example if the LED bulb is powered on and power outage occurs, the relay keeps the position. After power comes on, the LED bulb is powered automatically as the relay haven't changed the position. I have found this relay:
Is this relay fits my requirements? This relay is SPST-NO, but I can't understand why does that matter on latching relays (why does it matter if its NO or NC) because I can change relay state and leave it until I want to change the state again? Also, can I even send signals from Arduino directly to this relay, or I should choose 5V relay instead of 12V?
Yes, you can do all that, but you mention a power failure. After a power failure, how will you Arduino know the current setting of the relays?
How many amps is the relay conducting? It's very likely that you can get a cheap logic level power MOSFET to do the job. Unlike BJT's, MOSFETs use no current to keep the gate open -- only voltage must be present.
AVR chips EEPROM is guaranteed for 100,000 writes. Here is from the ATmega328 datasheet:
High Endurance Non-volatile Memory Segments
– 32KBytes of In-System Self-Programmable Flash program Memory
– 1KBytes EEPROM
– 2KBytes Internal SRAM – Write/Erase Cycles: 10,000 Flash/100,000 EEPROM
– Data Retention: 20 years at 85°C/100 years at 25°C(1)
