Board aliexpress

what do you think of this board for machine control?

It looks interesting but the Pro Mini doesn’t even have a USB connector but if you can find an Ethernet add-on for the Pro Mini then you could use UDP.

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or just connect a hc05 bluetooth

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If this is your first build i would stick with the genuine arduino nano.

Ali Arduinos do work, but sometimes they have “special issues” with interfacing with them.

The aliexpress 485 relay boards are already supported by @GoRoNb and his smd board variant.

ModbusRTU/RS485 is indeed a perfect choice due to its robustness, so it’s true, I provide a vitural COM port for RS485 onboard. This means, the RS485 is fully under control of the PC/tablet, which has to provide the data. On my Git page is demo code.

Where can I get a DPDT relay board for 8 or more relays?

Here e. g. You can put up to 32 of those modules on one RS485 bus.

But I need this type of contact.
For older sprayer controllers, this type of relay is ideal for automatic control. It is enough to cut the path to the pcb and solder the outputs from the relay. Unless there are better ways, e.g. for a mueller driver.

why not using two SPDT relays for each channel?

Theoretically, you can do it, but you need to modify the code and divide the signal by adding a small delay so that the 2 relays do not short-circuit. DPDTs would be good, they could fit in the controller housing. 2 * 8 is a bit of a big album.

you can use these Modbus boards and connect the coils of two relays together with a small wire. Whenever one relay is activated via Modbus, the other one switches as well.

Do you think they’ll never make a short this way? I have to try.

Here Signal Relay Module Board DPDT
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Hi, someone buy this board? which one specifically?