I have a project that is replacing 8 push buttons with relays. The issue is there is very limited space. Rather than using relay modules I am considering using the bare relay. What are the issues with this or any other recommendations
What are the buttons switching? Logic levels or power?
There are things to consider beyond whether thr relays are bare or part of a module. These include
- The voltage rating of the relays bearing in mind that the ESP32 is a 3.3V device
- The current required to operate up to 8 relays. How are they powered ?
- The need to put flyback diodes across the relay coils depending how they are controlled by the ESP32
Most likely You need at least a transistor driver, 1 or 2 resistors, a kick back diode for each relay,
- YES I plan on using 3v relays if powered by the ESP board but I can also power relays for external 5v.
- The relays operate only one at a time, a quick push/release
- The load is resistive type - are flyback diodes needed
The relay coil is inductive. That's where the flyback diode is needed.
Use these:
https://www.digikey.com/en/products/detail/panasonic-electric-works/AQY282EH/646349
@cdb0ewm
Very tiny, cheap, only need one external resistor, works with ESP32
Breadboard friendly!
So what is this resistive load that you control with "quick push/release"?
You get better suggestions if you give some specs.
Th draw is 12v and .25amp
You need some transistor circuit to drive the relay, so why don't you drive the load directly with transistor? 250mA briefly doesn't ask spacy circuit.
@cdb0ewm
No problem they can handle up to 500mA
Did I say they were cheap and tiny?
No diodes or transistors needed!
Thank you
Not a good starting point, microcontrollers are not power supplies, Especially mixing electromagnetic control and supplies..
Study the problem, then ask for advice without telling how they should be helping you.
Recommendations depend on the switch load and configuration.
Medium power low side with common ground? Use an octal power switch and it fits in a DIP18 package or smaller.
Low power with isolated grounds? Optoisolators. Possibly use a package with multiple ones to save space.
Low power with common ground? Can possibly use the arduino directly.
Design's in the details.
Thank you for your guidance and the drawing
You are welcome.