I am trying to make an electronic appliance. My circuit has 8Nos 5V components and 1Nos 12V component. (2 of them being Arduino Pro Minis). I have 3 questions regarding this circuit:

Q1: How do I design the power supply for this circuit? I can have only 1 adapter (wall wart) to wall mount this appliance.



Following is the list of my components:

  1. Arduino Pro Mini 5v/16MHz (Master)

  2. Arduino Pro Mini 5v/16MHz (Slave)

  3. DS3231 RTC

  4. 16x2 LCD + I2C

  5. Keyes 040 Rotary Encoder

  6. Relay (5v) - For Solenoid Valve

  7. Relay (5v) - For Flow Sensor

  8. Flow Sensor (5v)

  9. Solenoid Valve (12v)

Q2: Is it wise to mount everything on a single prototype board?

The circuit worked well on bread-board - behaves sporadically when all components are mounted on a proto-board.

Q3: Connected Question - How do I deal with memory leakage? Question to be dealt with later - once power supply issue is resolved.


Can someone please help me "unhold" this question?

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    \$\begingroup\$ Sorry, this is not sufficient info to even get started helping you. Add as much info about the system as you have. As you probably can imagine, it makes a whole lot of a difference what kind of components these are. \$\endgroup\$ – Marcus Müller Jul 16 '17 at 19:22
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    \$\begingroup\$ You figure out how much current each of the 5 V devices uses, add them up and buy a 5 V PSU with an amps rating >= your sum. Do the same for the 12 V devices. \$\endgroup\$ – Transistor Jul 16 '17 at 19:35
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    \$\begingroup\$ Since the 12V component is labelled "Solenoid Valve" look at its power consumption first. It's probably more than all the others put together. If so, use a wall wart to drive it at 12V, and a 12V to 5V switching regulator for the rest. Size the wall wart to power the lot, with some spare. \$\endgroup\$ – Brian Drummond Jul 17 '17 at 12:12
  • \$\begingroup\$ Yes - the wall wart is rated 12v. It is taken to an KA7805 - But for some reason the circuity works well on a breadboard. Once I solder them on on a proto-board - the lcd won't display anything most of the time and the rotory encoder won't respond. Once once in 10 times the LCD will show what it is programmed to show. \$\endgroup\$ – Pushkar Sheth Jul 17 '17 at 12:58
  • \$\begingroup\$ @MarcusMüller Sir - I have provided further details. Can you please "unhold" the question if you find the information enough? Thanks. \$\endgroup\$ – Pushkar Sheth Jul 18 '17 at 11:24

Basically you will need to make (or buy) a power supply module that can supply the required currents and voltages. This can be done in many ways, depending on the loads. If a low current and low cost is required, capacitive droppers may be used - but that means everything remains potentially at line potential. Galvanic isolation is probably a concept you should read up on..

The most realistic option today is switch mode power supplies. They provide galvanic isolation, and are efficient, cheap and compact.

The easiest DIY approach for a beginner is probably a linear power supply: a transformer, rectifier, capacitor, and voltage regulators. They require big transformers, have poor efficiency, but are extremely simple to grok conceptually.

If you add more specifics about your load you'll get better answers.

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