DIP-encapsulated micro relays to be driven directly from the microcontroller/ESP pin?
TL;DR
- A V23100-V4 dual signal relay was tested as a tiny mechanical disconnect for microcontroller and ESP-controlled lines.
- Its 500 Ω coil and built-in protection diode allow direct GPIO drive, avoiding an extra transistor in many DIY circuits.
- The datasheet lists 1 A contact current, 200 V maximum voltage, 10 W switching power, 3.5 V operate, and 0.75 V release.
- A 5 V test worked immediately, and an ESP32 at 3.3 V also closed the relay despite the 3.5 V operate rating.
- The 3.3 V result stretches the specification, so production designs should still follow the manufacturer's limits.
Generated by the language model.
Today a little tidbit I came across while developing one of my projects. I was looking for a simple way to mechanically disconnect microcontroller/ESP controlled lines, with a minimum of additional components. This is how I came across the very small V23100-V4 dual signal relays. Interestingly, the manufacturer explicitly emphasises in the documentation that the coil can be controlled directly by TTL signals, which is immediately appealing for projects with microcontrollers.
Consider the parameters from the datasheet:
- maximum contact current: up to 1 A
- maximum voltage: up to 200 V
- maximum switching power: 10 W
For such a small relay, these are quite reasonable values - especially when it comes to signal applications or small loads. The coil parameters are also interesting:
- coil resistance: ~500 Ω
- coil power: ~50 mW
This means that the control current is very low, which is precisely what makes direct control from the microcontroller output possible (at least in many cases). In practice, it is important to check how much current can be drawn from the GPIO. For example, for the PIC18F2550 it is 25 mA:
Assuming a supply voltage of 5 V, about 10 mA will flow through the ~500 Ω coil. Well under the limit. Just what about lower voltages? According to the datasheet note:
- closing voltage (operate): 3.5 V
- opening voltage (release): 0.75 V
These values suggest that the relay is designed with low-voltage logic in mind. However, an interesting question arises: in practice, will it also work at even lower voltages than the declared 3.5 V? There is often some design reserve in such components, so I thought I would give it a go with ESP. DIY projects have their own rules, it's not mass production, so you can afford to do more. So it's time for testing.
The whole thing has a standard DIP raster, so it fits on a contact board:
Leads - yes, there is already a protection diode inside in parallel to the coil, so you can't connect the coil in reverse either:
First test at 5 V - no surprise here rather, the whole thing works.
Second test - controlled from ESP32 at 3.3 V:
Here I've stretched the specification a bit, as the manufacturer announces the contacts close from 3.5 V rather than 3.3 V, but nevertheless the relay works too.
In summary , this was an example of a small relay that in practice turns out to be much more 'friendly' to microcontrollers than the datasheet note alone might suggest. Thanks to the very low coil power consumption, it can in many cases be controlled directly from the GPIO, without an additional transistor. Of course, in production applications it is better to stick to the manufacturer's specifications, but in DIY projects such a reserve of parameters can be very useful.
Undoubtedly this was a rather beginner's topic, but I hope it may have interested someone.
Have you used this type of relay in projects, and if so, for what?
p.kaczmarek2 wrote 14355 posts with
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Comments
The question is whether one is making something for art, for the desk. In such circumstances, one gets away with a great deal. For a product, especially one exposed to non-room temperatures, I would not... [Read more]
Right, but as I wrote in the next sentence - in production you should stick to these parameters and preferably with a margin, especially because if something goes wrong, a discrepancy of parameters on... [Read more]
This makes sense... The 5 V relay is often the only receiver on 5 V so it makes the design more expensive and larger. And that it devours a lot of current is less of a problem than a separate power supply.... [Read more]
In the IoT devices I have tested, I am unlikely to have seen opto-isolation in such an application, and we have shown a bit of these devices on the forum. Here's a dedicated search engine (each result... [Read more]
Where exactly did he write about this? TTL levels are ranges from 0 to 0.8 V for the low state and 2.4 to 5 V for the high state. In the table with the DS of this relay, there is a range from 3.5 V so... [Read more]
I was referring to this passage from the catalogue note: https://obrazki.elektroda.pl/7812401500_1776768079_bigthumb.jpg [Read more]
It is possible to control this way but this approach has some limitations. Firstly, you have to be careful with the sum of the input currents relative to the supply (ground or power) pin. Controlling... [Read more]