DIY Relay Module Saves Time | Hackaday

As any programmer can tell you, automating frequently performed processes is of great value. The more you use this process, the more it makes sense to automate or at least increase its efficiency. However, this rule is not limited to software; improvements in hardware design can also see improvements in efficiency. Therefore, [Hulk] designed

In his various other projects.

Although driving relays with transistors is basic, this project is not true

. It's about recognizing the things you have done too much and then designing from your project. [Hulk] can design a PCB with 12 modules, thus saving manufacturing costs. He can then easily fill them with specific components when needed. Another benefit of designing something like this yourself instead of off-the-shelf relay modules is that you can eliminate any useless functions you don’t need (or add functions that are not available in commercial equipment).

We are grateful

This will make our next project require a simple driver to install lights, garage door openers or any other binary electronic devices. Finding the correct transistors and relays, soldering them all on the project board, and hoping that they all work may be troublesome. Prefab solutions can solve all these problems, but we want to provide schematics so that we don’t have to design our own solutions.

We see it here, so there may be one there.

"Another benefit of designing something like this yourself instead of off-the-shelf relay modules is that you can eliminate all unnecessary functions that you don't need."

In this case, security seems to be that function. Without isolation wiring, the relay output is brought to a pin header connector that looks like a 0.1 inch.

To me, the relay contact connector looks like 0.2 inches (5.08 mm). May be suitable for screw terminals.

Both are suitable for low DC voltage. If you want to switch over, then SSR will be better.

For 120v, 0.2" is ok, but for 240v, it is a bit close, although I see many 240v connections with 0.2" spacing

What is the relationship between EMR and SSR and waveform related things?

Are you legally asking or procrastinating? In the case of asking reasonable questions, when they say alternating current, it is because the typical use case of alternating current is to use relays outside of industrial control devices, therefore, people who control the voltage fed from an outlet rather than from an AC source below 120V Among them, there is a large part of them. Therefore, I think the suggestion is more to make it stick to people's minds, and higher voltage (in the common case of using the line voltage of the socket) to use SSR.

For general relays, if you want to pay special attention to "whether it is used for AC or DC switching, you must carefully select the appropriate relay (for various reasons, including maximizing the life of the relay and the expected operation)" . I'll switch shortly after I tell you. "

So, anything related to EMR and SSR waveforms? Typical characteristics they think of:

Electromechanical relay

-Possible EMI/transient noise/electromagnetic coupling interference problems

-The change of the pull-up/pull-down voltage will produce high hysteresis, which may affect the precise timing

solid state relay

-Mechanical movement limits the switching time, which may affect the load-side waveform

-No load level switching function usually

-Produce lower EMI (usually)

-Lower hysteresis and faster switching time

– Normally, AC rated SSRs have a zero-crossing (synchronous) function, so they wait for the zero-crossing of the waveform to be turned on (this is good for many loads, but it will destroy the precise timing), and randomly turned on (asynchronous) will turn on immediately. I did not see There are no burst pulses and phase angles over AC load signals, but according to my experience, these are unusual. Although they are related to waveforms, I will not write too much.

SSR is also easier to kill, may fail due to short circuit and leakage mode, and requires a heat sink.

To be sure, SSRs have a place, but they are not the end of the exchange.

Look at any device that hardly uses proportional control and you will see relays instead of SSRs. There is a reason.

In addition to [Lord Binki]’s comment,

The original post was about the safety (distance isolation) of the higher supply voltage. I should make it clear that "AC" means power supply voltage.

In this case, SSR has other advantages for those who are not experienced in power supply voltage design

Built-in pre-calculated and certified distance isolation

Very high, safe, certified voltage isolation

The physical distance between the high and low voltage sides is large

Low drive current, usually can be directly connected to uC GPIO

The power-side screw terminal has a baffle to encourage tethered connections.

I am not sure whether SSR can solve all the problems. They do not wear out mechanically like relays, but there are more serious problems. They often cannot be closed. I think it is better to turn it on or off depending on the application, but the first one I thought of controlling the heating element, and turning it off might burn the house.

There are optically isolated relay modules, and the price is about $1. This DIY solution will cost more or less security than isolation modules.

I totally agree. Sometimes, as the process evolves, it becomes easier and cheaper. If you need to control a larger object, you can use an off-the-shelf photoelectric coupling relay module to pull in a larger contactor.

Some of them are designed to be used in the 90v-120v area and are not safe in the 220v-240v area.

It is a good thing that you must accumulate things you use frequently, and not get tired every time. A few days ago, I needed some LEDs so that I could debug the product built a few weeks ago, so I made an 8 LED module that can be placed on a breadboard (with SOT-23 NPN, some 0805 resistors and some 4mm LEDs) . My LED light can). I don't like the idea of ​​driving the LED directly, and I am tired of wiring many parts all the time, and it also takes up a lot of breadboard space.

I have tried this before, but on those single-sided copper Radio Shack boards. It is not that small (I used TO-92 and axial resistors), and the pads of the header will loosen and start to lift. And I don’t even know where it went. This time I got some double-sided feedthrough boards from Amazon. I hope they can stand up and use them. This is also a project where I can allow the board to gain more experience in using KiCad.

Now, I should make a switch input module, but this time the resistor and a big DIP switch have benefited me a lot.

This is similar to ULN2008, with some smd resistors and LEDs on a 0.1 inch pitch strip board. 8-pin right-angle connector and flying leads for power and ground.

You can use a resistor network to make it simpler.

ULN2803

To be fair, this is also the practice of SMT soldering, and the circuit prototype for future circuit board layout practices. SMT parts are mostly butted to each other on doughnuts with 0.1 inch pitch.

I also do the same thing: if I use the circuit more than twice, I will look for a cheap commercial version or make a bunch (or make a schematic/layout that can be copied/pasted into other layouts.) For me , It is such a low-side switch, a switching buck regulator and a low-side constant current driver. More and more arduino pro micros or esp32s are also stuck on everything, sometimes just in case I want to add intelligence in the future.

Why do you want to reinvent hot water.... a single relay module off-the-shelf...opto-isolation...less than a dollar...focus your energy and knowledge on things that don’t exist yet...

I think this "project" is actually just an invisible advertisement for the factory.

It's really all...

You really need to see how many times you have performed an action. I don’t use relay boards much-maybe 20 per year-and they only cost (the relay board I just looked at is similar to this), and the price is $0.27, while the photoelectric isolation price is about $1.50, One of them already comes with $8266, which is about $2, and I have to do a lot to build my own independent circuit board.

Of course, if I still do other things, I will put a relay directly on the board.

Mandatory XKCD

. I often feel guilty about it, so I put it in the office.

Since no one mentioned it, you must:

I see many people are keen to buy opto-isolated relay modules for less than $1

There is no doubt that these are the most popular products in major online stores in China. All the opto-isolated modules I have encountered are not opto-isolated, because both sides of the optoelectronic controller share the ground, and VCC is also very rare

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