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EDIT: Load side is build up like this :

ESP > Shift Register/Expander > NMOS > SSR DC > 3 x Pumps (uses V_in or external power supply via SSR AC)

ESP > Shift Register/Expander > NMOS > SSR DC > Heating Elements ( external power supply)

ESP > Shift Register/Expander > NMOS > ~8 Valves (500mA - 12V trying to get the Datasheet for them)

I can't choose between Shift Register (TPL9201 - higher mA for NMOS switching) or I2C Expander (MCP23008 - simple to use and cheap but low mA)

Everything that needs to use 5V (currently switched by a RPM5.0-2.0):

ESP32, LAN8720(+ RJ45 Module - Needs 3V3 but I get that from the ESP so I count it in here), maybe the MCP23008 + bunch of waterflowsensors YF-S201 and digital thermometer DS18B20


All my post kinda are about the same project so who remembers my name maybe knows why I am asking this. For the project I have to have a 12/24Vdc Input Voltage depending on the user and regulate it down to 12V and 5V. I learned here and somewhere else that simply the best method to do that is to use a Buck-Boost Converter from 12/24V -> 12VDC and a Buck from 12Vdc -> 5VDc. I use switching because I the load uses a min of 2A and max of 8A which just cost to much place for linear regulator cooling.

As I tried to simulate this a bit in SPICE and TI Webbench i stumpled over switching noise. My supervisor stated that he wants a stable voltage but doesnt specifiy if it has to be low noise aswell. On the load side I have the following :

~8 electrical valves, ~3 pumps, a bunch of SSR(DC and AC), an ESP32 who sends and recieves the signals(Ethernet added) some Shift Register / Expander for a bunch of NMOS who switch the valves and SSR.

I tried to read a bit abouse voltage/ switching noise and it only seems to affect ADC or audio signals. But in my layout I don't use this so would I need to care ? Also what about PCB desing, do I need to watch for extra short routes on the noise affected lines like I need to watch the Ethernet 50Mhz osz?

Thanks for any help!

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  • \$\begingroup\$ Most likely you are fine without special measures. But still filter power and route shortly for the sake of EMI. Otherwise, you really do need spec for tolerable noise/ripple and supply impedance to find our if the regulator noise/ripple and output impedance are fine. Also pay special attention, in case your regulator uses different regulation modes at light/heavy loads. The ripple and frequency can be substantially different. For general purpose digital parts and little logic, several 100 mVs ripple can be fine. \$\endgroup\$ – tobalt 2 days ago
  • \$\begingroup\$ Be more specific about 12V load specs & tolerances. Pumps can start up drawing 10x the current and SMPS do not like that. Can you be more precise on load specs? You either need overkill to start pumps, allow sag when starting, have a slow startup, or use a battery as a 10kF supercap and charger \$\endgroup\$ – Tony Stewart EE75 2 days ago
  • \$\begingroup\$ Your supervisor should know better to give you specs to help you get started \$\endgroup\$ – Tony Stewart EE75 2 days ago
  • \$\begingroup\$ Added as much information as I could on. I dont think I have to worry about the pumps as they use the stable voltage either from Vin or external. \$\endgroup\$ – Daniel Do 2 days ago

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