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Phil23
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Joined: 27/03/2016
Location: Australia
Posts: 1667

Posted: 01:13am 23 Jun 2016

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Hi all,

Is this a completely incorrect scenario?

Using 3 of Geoff's Backpacks.

Still on breadboard at this stage and powered by a module with 5.0 & 3.3 Volt rails,
AMS1117 Regs, 800mA rated from memory.

Just looking for feedback before I rebuild it on some proto board.

The 5V rail feeds the backpack, powers the bus for the 5 DS18B20's & the 6 relays for pumps & motorised valves.

The 3.3V rail on the external module powers the RTC & an ESP-8266.

The Backpack's 3.3V reg only powers the MicroMite.

I'd rather not remove the backpack's MCP1700, but realise it's probably pushing it up hill to power the ESP's & RTC as well as the micro with it.

The negative rails are all common, but the two 3.3V rails V+'s remain separate.

Is this grossly incorrect & going to cause me headaches?

Thanks

Phil.

Grogster

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Joined: 31/12/2012
Location: New Zealand
Posts: 9589

Posted: 01:33am 23 Jun 2016

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So long as both 3v3 regulators are sourced from the same supply voltage, and have a common ground, there should not be a problem - essentially 3v3_1 and 3v3_2. Personally, I like to use a juicier 3v3 regulator and put EVERYTHING on the one regulator, but I can see why you want to do it that way.

I don't see their being any issue with multiple 3v3 regs if necessary, so long as they are all powered from the same supply voltage and are all ground-referenced to the same source supply.

Smoke makes things work. When the smoke gets out, it stops!

WhiteWizzard
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Joined: 05/04/2013
Location: United Kingdom
Posts: 2932

Posted: 05:10am 23 Jun 2016

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Phil23 said . . . The negative rails are all common, but the two 3.3V rails V+'s remain separate.

Is this grossly incorrect & going to cause me headaches?

The scenario you describe is fine.

You can have as many separate PSUs as you like powering different parts of the circuit as long as all are referenced (i.e. connected) to the same 0V (or GND, -ve if you prefer these 'names', . . . ).

IMHO it is good idea to have a 'dedicated' LDO powering the PIC, and another vReg drive more 'dirty' components (such as motors, relays, ESP modules).

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