Powering Multiple Vavles,Pumps & Heater with one buck converter


#1

Hi Friends,

I am trying to power 4 of the adafruit solenoid values (12 V, 0.2-0.3), two pumps (1- 12V 5A, 2- 12V 0.3 A) and a resistive heater with left over power. My question is, is it possible to use one AC DC buck and somehow separate the power using voltage dividers or something. I don’t have much experience splitting power so any suggestion means a lot.

Thanks


Switching Power Best Practice: Photon driven MOSFET's
#2

I’d start with the highest voltage you need, and then work your way down with voltage regulators/linear regulators. I wouldn’t fiddle with voltage dividers, since those would need to burn a lot of voltage then, not really efficient, though it might be able to double as your resistive heater :wink:


#3

You have to be more specific. You can power them all from the same supply if the supplied voltage of the source is equal to the required voltage of the loads. In your case, you didn’t tell us the required voltage of the heater, but the rest of the loads can be powered from the same 12 V supply. Your power supply has to be able to supply your worst case scenario current (all the devices turned on at the same time). For this, you have to add all the maximum currents of the loads and make sure your supply can deliver at least as much current.

As far as I know, there is no such thing as an AC to DC buck, so I don’t know what kind of power supply you are referring to. I also don’t know what you mean by ‘left over power’ or ‘splitting power’.


#4

@jjlee32, adding to @stelian’s post, if I understand correctly, you want to power the following:

12V inductive loads

  • 4 solenoids, 0.3A each (max total 1.2A)
  • 2 pumps, 5A each??, max total 5.3A??

12V (???) resistive load

  • Heater, ??? A

5V

  • Particle device, max total 0.5A

Getting a more detailed set of load characteristics would be helpful.

The inductive loads will require surge current capability while the resistive load less so. Since it looks like you are using an AC supply, you may want to look at a ATX (PC) power supply. You can get smaller versions like this one from Aliexpress for example. These types of supply provide plenty of current and lots of protection.

You will need to design your control hardware (power FETs, etc) carefully when driving your inductive loads so as to protect your hardware from surges and flyback voltages. Your wiring will need to be sized to the current demands as well. :wink:


#5

Thanks all,

Sorry i wasn’t clear enough in my initial post, heres a list of the components i’d like to power with one AC/DC converter.
-4 adafuit solenoid valves (12v , 300 mA)
-1 peristaltic pump ( 12V, 300 mA)
-1 high pressure pump (12V 5A)
-1 resistive heater (whatever is available)
-and the particle device

I have a small understanding of the inductive loads that could surge back from turning on or off pumps (i think its called back emf), could this be as simple as introducing diodes?

Also i think ill be approaching the upper limit as far as breadboard amperage capacity. Any suggestions on how to handle this dilemma. Thank you all for your informative responses so far.


#6

You need some power MOSFETs to drive the loads. As you said, each load should have a kickback protection diode across it. Assuming that you want to drive everything from a particle device, you can’t connect the mosfet gates directly to the particle pins because the 3,3 V logic level is too low. For that you need a MOSFET gate driver that boosts that voltage to around 12 V. Something like this should do :

You could build one of these on a breadboard, test it with lower currents and if it works, build more of these on a perfboard. If you think it’s too complicated, look online for ready-made modules.

As @peekay123 said, an ATX power supply could power all these.


#7

Thanks all for the great information


#8

Okay friends,

I think i have it all sorted out but want to be sure before i make the purchase. I made a simple excel spread sheet to calculate the worst case scenario power consumption, ill try and throw a screen shot below. excuse all the spelling errors…

So i rounded up to 150 W, 12 A which seems to be a common pair. Now from what i’ve learned so far from this post, it’d be best to use a small PC power supply, so i found this one, which fits my constraints, will this one work?

If it will work, from the photos it look as if their are only a few connection ports, how would I spilt the power to get all of my components the necessary power? This seems to give the required power in one lump sum, and the power output seems to high for a breadboard. I hope i made my problem clear enough for you all to tell me what I am doing wrong.

Thanks in advance.


#9

@jjlee32, your system needs to power supply voltages: 12v and 5v. The 12v supply you chose is fine for the 12V side but you will need to regulated that down to 5v for the Photon and relay board. The supply you chose is not a PC supply, it is designed for LED lighting. It looks like that supply have two feeds, each rated at 6.25A though it’s hard to tell. Not sure they can be combined into a single 12.5A feed.

In order to get the 5v you need, you could just use a simple linear regulator like a LM7805 or LM1117 to step the 12v down to 5v.

.


#10

Have a look at the link below - this uses a Particle Photon to control two flow meters, an electric pump and an optional pressure transducer as part of a school / University experiment. Similar to what you are doing.


#11

Okay Update:

I have purchased the power supply and wired it all up using an old 3 prong computer cord that i was previously using for an outlet. I have been looking into linear voltage regulators and was wondering the difference between those and a MOSFET? From what i understand MOSFET’s are essentially solid state relays, and are often used with Arduino? (please correct me if i’m wrong).

Specifically the TIP120 seems to be poplar for low voltage controllers like the Arduino or photon. My question is could these transistors replace my relay board and also serve as the linear voltage regulator?


#12

You need some power MOSFETs to drive the loads. As you said, each load should have a kickback protection diode across it. Assuming that you want to drive everything from a particle device, you can’t connect the mosfet gates directly to the particle pins because the 3,3 V logic level is too low. For that you need a MOSFET gate driver that boosts that voltage to around 12 V. Something like this should do :

Just an FYI, this is not entirely correct. there are a bazillion logic level fets out there in which you can connect to the particle.


#13

A MOSFET and a linear regulator are two very different things. A MOSFET is a transistor, which is often used as a switch, but you can’t use one as a voltage regulator. If the power ratings of the MOSFET is adequate, and you’re switching a DC current, then yes, it could replace a relay.


#14

Thanks Ric, So I have not a 150 12V power supply that was meant for LED lights but am trying to get it to power all of the system components. So if i have 12 V DC up to 6 A (i think) per terminal.

Can i use a MOSFET connected to a pin on the photon to switch this power. My plan right now, granted i’m super novice, is to get a bunch of linear voltage regulators rated for the necessary power for a given component, and then run the regulated power to a relay that is controlled by the pins on my controller.


#15

Update:

I have decided to go the MOSFET.I’ve used some other posts as a guide specifially these;
https://community.particle.io/t/n-channel-mosfet/?source_topic_id=33583
https://community.particle.io/t/controlling-fan-speed-with-photon-and-fet-transistor?source_topic_id=33583

Now i have a simple circuit sketched in frizting which ill attach now;

I haven’t wired it up yet as i’m still waiting for some parts but i wanted to post it here for it to be sanity checked and critiqued. I plan on having more than one of these valves ( and other components) connected to the power supply, and i still don’t know how to do that as my power supply only has two terminals. Do i run one to a power rail and just use the LVT’s off the rail?

I hope this post helps more than just me understand the underlying principals.
Thanks in advance.