How to control F&F relays on DIN rail with ESP8266?

Question

Welcome, I would like to do a lighting control in my house, and to make it look nice I would like to use DIN rail mounted F&F relays. The problem is that they have a 24VDC coil. Controlling from the ESP8266 is a bit of a problem in this case. Can anyone recommend anything on this subject? Some...

jakubek56 · Answer

Even if the coils of this relay were at 3.3V they would still draw too much current from the ESP output. The only solution is a transistor. Using a PLC instead of an ESP AND a transistor is several tens of times more expensive.

shady79 · Answer

does anyone know any ready-made modules with transistors that could be used? Making such a board isn't too much of a problem, but if there was something ready-made and with e.g. MCP23017 it would be a great thing:) .

Anonymous · Answer

On ali there are single and dual channel modules with optocouplers (necessary in this case) with 3V3 logic control. Images below - you need to search under Optocoupler Isolation Module Driver for the 3V3 version. . . Added after 38 : . I couldn't find any such.

tos18 · Answer

MCP + ULN2003A

shady79 · Answer

well this is an interesting option.

krzbor · Answer

To control a 24vDC relay all you need is one transistor, a 1k resistor and a diode for the surge on the relay. I don't know why separate modules are needed. Such a thing can easily be assembled on a universal board. I don't know how you want to build a circuit based on ESP and where to get power for the relay (24V) and ESP (3V). I personally switched to SONOFF modules, e.g. Sonoff Basic. They can be freely reprogrammed and have what you need: power supply, ESP and relay. There are even DIN rail mounts for Sonoff. I recently bought (but haven't installed yet) a Shelly 1 - that's a baby! Fully programmable too, of course, it even has a programming socket soldered in. But beware - the chip has no galvanic separation.

Anonymous · Answer

. What model of relay is this specifically? . Then there will be no galvanic separation either.

krzbor · Answer

The author writes nothing that he wants to have separation. Anyway, what is the point of separation if you are controlling a relay?

Anonymous · Answer

. To galvanically isolate the 24V supply voltage to the relay coil from the 3V3 logic. Added after 7 [minutes]: . This is some sort of option. Then the F&F relays seem superfluous and there is no problem of galvanic separation . There are even commercially available 4-channel sonoffs with DIN mounting. .

krzbor · Answer

Just what for? We short the negatives of the ESP supply (3V) and the 24V supply and connect to the emitter of the transistor. A 1k resistor to the base and then to the ESP, and a relay to the collector, and the other end of the relay to +24V. This is a typical operating circuit (OC) that can cope with different voltages.

Anonymous · Answer

As long as the transistor does not fail and there is a 24V breakthrough towards its base and then towards the ESP output pin. The relay coil alone will not be sufficient protection. Of course, there are those who claim that they have not used optocouplers in this kind of control circuit for years and nothing bad happens. Let everyone do their own thing.

krzbor · Answer

24V relays usually have low currents. You can give a 10k resistor in the base of the transistor instead of 1k. Then, in the event of a breakthrough, we have (24V-3V)/10k =2.1 mA - this is how much will flow through the uP output protection diode. Such a current will not damage it. Nor will it damage the ESP.

Anonymous · Answer

. I suggest that the colleague pull up the ESP output with a 10k resistor to 24V. Turn on the circuit for a dozen or so seconds and report the result of these tests.

shady79 · Answer

today i found this relay on alii, which i think can be controlled directly from esp

Anonymous · Answer

. Yes, this is an SSR with galvanic isolation from the control circuit.

shady79 · Answer

Hi again so as not to start a similar topic let me ask here on the subject of relay control via esp. I have connected the mentioned ESP and actually one of its pins via a PC817 optocoupler to the SSR25DD relay and switching on/off via it the 12V circuit with the LED strip works. On the other hand I have a problem getting dimming via a PWM signal. I have easyesp installed on my esp and when I give e.g. pwm 5.1023 it shines at max but when I give pwm 5.500 it also shines at max a fill of 100 shines say 10% less than at max and a fill of 20 does not shine. It can be concluded that the diodes basically do not react to the changing fill of the pwm signal. What do you think, should I look for the cause from the software side or could this signal be distorted somewhere. There are two optocouplers on the way, the pwm signal is generated by esp at 1kHz as standard. . I wonder if sometimes this R1 is not too small because it looks like in this case the current is limited to 33mA and the current capacity of the port is 12mA so it would be better to use a resistor in the 330-660ohm range to jerk the current from it to the max

tos18 · Answer

These relays have a response time of 1ms so the PWM frequency must be less than 100Hz because the relay will not handle it. R2 in my opinion is unnecessary. Consider ditching the SSR in favour of a good mosfet and driver - they will certainly be faster.

Anonymous · Answer

Yes, as colleague @tos18 wrote above, MOSFET transistors, not SSR relays, are used to adjust the intensity of the LED strip (dimmer). Example of solution:

shady79 · Answer

And this ssr is not made on a mosfet?

tos18 · Answer

It probably is - maybe even on two of them. which doesn't change things - a response time of 1ms.

Anonymous · Answer

. That much is clear from the manufacturer's note: . As you have additionally used an external optocoupler at the input, the response time of the circuit has increased. Added after 8 [minutes]: . Reduce to 100Hz (in ESP Easy less will not be set for PWM) and check. By the way you will already observe the LED flicker.

shady79 · Answer

can the frequency be changed somewhere in the settings or with a command, because I think I read somewhere that you have to change it somewhere in the source file, recompile the program and put it into esp.... Added after 8 [minutes]: . good i think i have found PWM,,,, Added after 44 [minutes]: I'll check tonight, but just thinking about it, a time of 1ms is 1/1000s so a frequency of 1kHz is theoretically within that range. Maybe it would be enough to give for example 800Hz?

How to control F&F relays on DIN rail with ESP8266?

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