Best way to increase amperage?

EDIT: Please check out my response on this thread as I got a few things wrong or didn't even mention them in this post

Hello,
I am currently trying to make my fan smart with an esp32. Unfortunately, I now realized that the fan's power supply is only providing 5v at 0.07 amps to the controller - this may have been enough for the old microcontroller, but it cannot power on an esp32. So I already spend 20+ hours programming the software for the esp32, only to now recognize that I can't use it without modifying the power supply of the fan - which is exactly what I am now trying to do - but I don't know that much about electronics, so I got no idea what the best modification would be.

So if you have an idea, please feel free to share it with me. I also attached pictures of the power supply and marked the pins that output 5V to the microcontroller.



Hello SirM,
Welcome.

Please can you follow these instructions for the images as many of us do not want to go off the site to look at information that could be posted here
How to post an image

Thank you.

Thank you :slight_smile:

How do you know it can only supply 70mA?
How much current do you need?

There’s no simple way to increase the output current of an existing, ready made power supply. The simplest thing is to use a bigger power supply. If you need 5V then a cell phone charger with a USB output will be fine. I make a point of collecting old power supplies from electronic kit that’s being thrown away, I’ve got loads of them, I won’t ever use most of them but I always have a power supply handy. I suggest for the future you do the same.

I don’t know that much about electronics

Is there mains involved? I ask because it worries me when people who don’t know much about electronics mess with mains, easy way to an early grave…

How do you know it can only supply 70mA?
How much current do you need?

Hmm, I've actually found out that I measured incorrectly.
When I connect the esp to the 5V from the fan power supply and measure correctly with my multimeter it now shows 0.024 amps and if I measure the consumption of the original microcontroller it shows 0.003 amps. However, when I plug the esp into a known 5V 1A power source it shows an average of 0.170 amps with peaks of 0.3 which is in line with what I read online about an esp32's power consumption.

I also thought if I could just desolder the existing parts for the PSU and replace it with an old phone PSU, but yes there is main power involved that also worries me too. So I thought it would be better if I ask first if anyone knows of a better solution.

I also wonder if I can just replace a power supply with a one that provides more amps. I still don't know exactly which parts of the circuit board are intended for voltage conversion and which parts belong to the buttons and transistors that control the fan - what especially confused me is the transistor part because to me it looks like the transistors are switching only 5V.

This is just all I already know about how this circuit board works:

  • The two cables on the top are main voltage in
  • The 6 wire cable bundle on the bottom is intended for the buttons that output GND when pressed, one button is not installed
  • The 7 wire cable bundle on the bottom is intended for the transistors, one of them is not installed, the other two wires are supplying the microcontroller with GND and 5V.
  • The 4 cables on the site are intended for the fan motor and are controlled by the transistors that emit current when GND is applied

I am also sorry for writing so much and referring to the PCB on the images as "power supply, board, and circuit board" this is a bit confusing, and thank you very much for the help. Also, tell me if the project is too dangerous or difficult then I'll leave it alone until I know a lot more about electronics.

Unfortunately, I now realised that the fan's power supply is only providing 5v at 0.07 amps to the controller - this may have been enough for the old micro-controller.

There is no micro-controller in the photos, so either the fan does not have a micro-controller or there are more parts you have not shown.

Based on your description and the photos I was going to say there is no power supply in the photos but I'll change that to if there is a power supply from mains to 5V then it is the most crude and possibly dangerous power supply I have seen in a very long time. There is nothing to isolate the mains from the rest of the board. I am guessing this is either 40 years old or built to a design that is 40 or more years old. My best guess is that it uses a resistor and capacitor to drop mains voltage, which is both crude and dangerous. It certainly does not provide the stable, regulated power that a micro-controller needs. You can't just replace the power supply components on the board, even if you do it will still be dangerous and still won't be regulated.

If this were my project I'd scrap the existing controller completely and build a new one with a proper, isolated, ready made main to 5V power supply and proper, isolated switching for controlling the fan.

It worries me that you are even doing this with your limited knowledge of electronics, it is pretty clear that you have already done things that were dangerous and I don't imagine you realised the danger.

I strongly recommend you abandon this project for a few years until you have enough knowledge that you look back at this and shiver with the thought of how dangerous it was and how close you came to killing yourself. Seriously. Either that or find a friend who does understand the risks and how to mitigate them and have your friend supervise you.

Hi,
Is that PCB at mains potential?
What supplies the 5V for the old controller?

If it uses capacitive dropper from the mains then, STOP
I means your project can and possibly will be at mains potential.

How is the current controlled for the fan?

Can you please tell us your electronics, programming, arduino, hardware experience?

Thanks.. Tom... :slight_smile:

I don't think it must be so old device. AFAIK as long as the electronics is inside a plastic enclosure it should be safe even without isolation. It is a common design of hair dryers, vacuum cleaners etc.

For me it looks like a capacitive power supply. The voltage regulation is not so poor (notice the large electrolytic cap and Zener diode). It is possible to modify it to get more power but I don't think it is a good way.

  1. You need to understand the circuit perfectly - letal voltages are involved.
  2. You need to replace nearly all parts of the power supply (the capacitor surely, also the Zener diode with one with much higher power rating; the resistors very likely).
  3. The new components will need to be much higher value, much larger, much more expensive.

A better way is to let the power supply as is (in case something else needs it) and add a phone charger to power the ESP. It should be possible to choose some small and connect it to the mains inside the fan housing so you don't have two wires to plug.

In any case be very careful with the circuit. Never touch any part while connected to mains and give it some time (a few seconds should be enough) to discharge caps after disconnecting!

I have made most of my house 'smart' using mostly ESP products. I would not even begin to try to use the old controller.

I am betting that the fan housing itself is plastic because the mains power is in no way isolated from the other circuitry on the board. In other words, there is no way you can touch anything metal.

If all you want to do is on-off, then look at the Sonoff Mini.

Ok. From what I read I decided now that it is just not worth risking my life to eventually turn my fan smart, guess this is a pretty wise decision. So I will abandon this project and I’m not even sure if it’s worth going ever back to this project.

But I am still very interested in electronics, so I have got an old LED strip that runs on 12V and a suitable power supply (which is in an enclosure that I definitely won’t open). So I think this will probably be a safer and more beginner-friendly project.

And yes, the fan is in a full plastic enclosure you can kinda see it on the photos and I actually bought the fan about three years ago on Amazon for around 30 €. The microcontroller is not shown in the photos, I did not thought that it was worth showing as it was clear from the start that I couldn’t use it, but I wanted to use the existing power supply, buttons, and transistors. And just if anyone is interested in the “old” microcontroller, it was a Sonix sn8p2612pb which gets his power directly from the pins I marked on the photo.

I also want to add is what I don’t exactly see were opening the fan, while the it was disconnected from the power source was dangerous. Yes, I knew what I have to wait sometime time after disconnecting the fan before getting to those capacitors and that’s exactly what I did. And when I tested my prototype, I already figured out how the microcontroller part of the fan works and which pins are there for what.

Is that PCB at mains potential?

My last question is what does he mean, the PCB got a direct 230v wall connection and it is a European plug so GND and VCC are not fixed - if you mean that.

Can you please tell us your electronics, programming, Arduino, hardware experience?

Well, there isn’t much to say, this is the first “Arduino” project I wanted to turn in reality. So I designed a simple prototype with the esp, which was supposed to take over the function of the old microcontroller, it worked except for the missing power source. And I also started writing the software so I could see if I could get the result I wanted. And that’s it, and I only started this project because I thought that I could just replace the old microcontroller with my esp - so that I don’t have to mess around with any voltage above 5v.

So thank you for your help, I definitely learn a lot about hard and software - and also that I don’t know very much about these things.

My last question is what does he mean, the PCB got a direct 230v wall connection and it is a European plug so GND and VCC are not fixed - if you mean that.

It means is it directly connected to the mains, I think we have established that it is, therefore it is live and dangerous when powered.

Another option to consider is to use sleep modes for the ESP to reduce overall current draw and add a small battery to cover the increased power consumption while it needs to be active. The battery will recharge while the ESP is sleeping. As a quick, dirty and quite safe solution I would try 4 NiMH battery cells (probably taken from a rechargeable 9V battery) trickle charged simply via a resistor to the 5V.

Or maybe a large electrolytic cap (with an optional buck-boost converter) would be enough - it depends how much space is available.

Included is a text explaining transformerless power supplies. Since the difference between the mains voltage and output voltage is so large they can be viewed as a constant current source. And the Zener diode shunts any excess current providing voltage regulation.

Transformerless Power Supply Design.pdf (562 KB)

SirM:
The microcontroller is not shown in the photos, I did not thought that it was worth showing as it was clear from the start that I couldn't use it, but I wanted to use the existing power supply, buttons, and transistors.

And is where you failed so badly!

In order to "reverse engineer" a piece of equipment, you have to understand how it works. In the case of your fan, that information is contained in the microcontroller board, so that is the part that would need to be examined - in addition to the board you have. As far as we are concerned, unless you provide that information (whether or not you believe you know it), you have not properly detailed the actual problem. :cold_sweat:

You claim to have determined how the microcontroller works and implemented an emulation and you even say that "it worked except for the missing power source" but how can that be? :astonished:

SirM:
My last question is what does he mean, the PCB got a direct 230v wall connection and it is a European plug so GND and VCC are not fixed - if you mean that.

A mains plug does not have "GND and VCC". Neither main terminal is ground; there is a third terminal which is Protective Ground.