Question regarding multiple voltage regulators together. I have a project that I supply 24 volts for. I have one voltage regulator that goes from up to 25v down to 5v and another regulator that takes up to 15v down to 3.3 v. I need 3.3volts. using simple terms, is it okay to hook the 24v up to the 5v regulator's input then run its output to the 3.3v regulator (and then that "output" to my project)?
I understand it's not just input and output just trying to keep it in simple terms. Any help is appreciated, feel free to ask for clarification! Thanks
The 5V regulator must handle the load current plus the current of the 3.3V regulator.
The 3.3V regulator must handle the load current.
You must use capacitors as specified by the manufacturers.
The 3.3V regulator must be able to work from a 5V input.
The 5V regulator must be able to work from a 24V input.
I am using 7805 regulators. The 24 volts power supply would have a load of about 5/6 amps on it at maximum usage. What I am doing is powering a 10 meter RGB LED strip ( not 2 strips of 5m, one 10m ) with its supplied 24 volt AC -> DC power supply. I want to drive the strip's red, green, and blue channel from a nodeMCU ESP-12E board. I have the output of the nodeMCU pins connected to some TO-220 MOSFETs and I would like to supply power to the nodeMCU from the 24 volt adapter but the nodeMCU accepts only 3.3volts and as of now the only regulators I have are a 5v (that takes up to 25 volts) and a 3.3volt (that accepts up to 15 volts). If this is too complicated/not efficient I could just drive the nodeMCU from a much lower voltage power supply through the 3.3 volt regulator. If any of these techniques are unsafe or unusually inefficient please let me know! Thanks again
I thought you said you are using 7805 regulators, yet you say your regulators input voltage ratings are
25V and 15V respectively, whereas the 78xx family has an abs max voltage rating of 35V.
I know the AP1117 3.3V regulator is low enough dropout to run from 5V input, but has an abs max of 18V
in the input.
A dc-dc converter from 24V down to 5V followed by a 3.3V AP1117 seems a reasonable way to go.
My apologies, the 5 volt regulator is 7805, and according to the specs from where I bought it says max input of 25 volts (typo?) but the max I would run to it would be ~ 24 volts. The second regulator is an LC1117V33 that has a max input of 15 volts according to site I ordered it from. Thank you for your suggestion. At this point am I getting to the point where this is more complex than it needs to be and should I just power the nodeMCU from a seperate supply? (Just didn't want a lot of external wires but wouldn't be that big of an issue)
Also, should I be running heatsinks on these regulators and/or mosfets? It would never be used for more than a few hours at a time and very very rarely at max white.
bmoe24x:
My apologies, the 5 volt regulator is 7805, and according to the specs from where I bought it says max input of 25 volts (typo?) but the max I would run to it would be ~ 24 volts. The second regulator is an LC1117V33 that has a max input of 15 volts according to site I ordered it from. Thank you for your suggestion. At this point am I getting to the point where this is more complex than it needs to be and should I just power the nodeMCU from a seperate supply? (Just didn't want a lot of external wires but wouldn't be that big of an issue)
Also, should I be running heatsinks on these regulators and/or mosfets? It would never be used for more than a few hours at a time and very very rarely at max white.
Thanks again
So you have a 7805 and an AP1117 3V3... Yes, you are right, the recommended maximum working input
voltage for the 7805 is quoted as 25V (abs max 35), but in practice its very inefficient to drop that far in one
step without using a switch-mode converter. If the current is small it may not be an issue, but we don't know
what current you are going to need.
do you mean 5/6A or 5 to 6A? Because in the latter case, this discussion should take a turn.
With any linear regulator, you just burn (Vin-Vout)*I. In your case, that would be 114W!
You definitely need a buck converter instead and at 6A, that is nor you common Aliexpress 2$ thingy. You might consider just changing your supply to a 5V one or consider splitting the strip.
MarkT:
So you have a 7805 and an AP1117 3V3... Yes, you are right, the recommended maximum working input
voltage for the 7805 is quoted as 25V (abs max 35), but in practice its very inefficient to drop that far in one
step without using a switch-mode converter. If the current is small it may not be an issue, but we don't know
what current you are going to need.
The current the NodeMCU draws should never be more than 1 amp max ( I believe for my purposes at least.. ) but the current that the power supply would have drawn from it could be 5 or 6 amps.
ElCaron:
do you mean 5/6A or 5 to 6A? Because in the latter case, this discussion should take a turn.
With any linear regulator, you just burn (Vin-Vout)*I. In your case, that would be 114W!
You definitely need a buck converter instead and at 6A, that is nor you common Aliexpress 2$ thingy. You might consider just changing your supply to a 5V one or consider splitting the strip.
5 or 6 amps. 300 leds per 5 meters and there is 10 meters ( I will never drive them at all 3 channels 255 though ).
By changing my supply do you mean to power my NodeMCU with a 5v supply and then a separate supply for my LED strip or a 5v supply for it all? Because the strip's specs require 24 volts.
bmoe24x:
By changing my supply do you mean to power my NodeMCU with a 5v supply and then a separate supply for my LED strip or a 5v supply for it all? Because the strip's specs require 24 volts.
If 24V are the specs of your strip, than the current going through the is in no way relevant for your voltage regulator. Why did you give us that when we asked for load? Are you fully aware how voltage and current works?
If you just want to power just your NodeMCU, then you don't need 5V. Get an MP1584 to bring the 24V to roughly 5V (at least 4.7V, not more than 8V) and then add your AP1117 (and the specified caps for that) to get to 3.3V.
ElCaron:
If 24V are the specs of your strip, than the current going through the is in no way relevant for your voltage regulator. Why did you give us that when we asked for load? Are you fully aware how voltage and current works?
If you just want to power just your NodeMCU, then you don't need 5V. Get an MP1584 to bring the 24V to roughly 5V (at least 4.7V, not more than 8V) and then add your AP1117 (and the specified caps for that) to get to 3.3V.
My apologies if the information I provided was unclear. I thought I stated that the power was going to the NodeMCU which should never draw more than 1 Amp (probably much less actually).
ElCaron:
yes, that works, too. its smaller than my suggestion, but also about 5 times the price.
Okay I will try that. Space will be a priority if I finalize this project into a permanent solution. I was able to get it for about $3 from an electronics supplier near me. Thanks for all the help