Hello, this is the first board I have made. I plan to make more in the future, but first I would like to hear recommendations or comments from people more experienced in this to make sure I've done it right.
This is the control board for the main hydroponic pot systems, namely the circulation pump, the two peristaltic pumps and the solenoid valve.
--- The controller is an ESP32-WROOM, I made it removable using two HDR-F2.54_1x15 connectors (they are signed on the board as H1, H2).
To control the pumps and the valve, ---- MOSFET transistors are used (by control I mean ON/OFF as well as PWM), with 100 ohm protection resistors and a 10 kOhm pull-up resistor connected to their gates. A diode is also used to protect the transistor from reverse currents.
Pumps and valve are connected to terminals CN1-CN4 (the highest current on one terminal is up to 700 mA).
The terminal carrying the main load, CN5, is supplied with 12 V DC voltage. The current at switching on all consumers is 3 A. It is through this terminal that the entire board is powered.
---- The step-down DC/DC converter (located on the bottom layer) is also powered from CN5. The converter powers ESP23 as well as the three connectors NX1,NX2,NX3 for connecting the ultrasonic level sensors.
The transistors and the whole circuit have been tested on a breadboard, everything works. Please give me your thoughts on how I have arranged the board. The project is developed in EasyEDA, I also provide its archive.
The 10k resistors should connect to the other side of the 100 ohm resistor.
Now they form a voltage divider, which will reduce gate drive a bit.
Not very important, but easy to change. See this page.
Leo..
Good evening. I chose the transistor by availability in the market and taking into account the possibility of fast delivery, also attracted by its price.
IRLML2502 is a cool option for PCB but not suitable for breadboard at the time of debugging. But I will definitely consider installing it in the future. Thanks for the idea!
If you have any comments about IRLZ44N I will be very glad to listen to them, as I am new to this.
Good evening. The idea is interesting, but will this change affect the operation of the circuit?
So far you are the only one who has come up with this idea, I have looked at websites but have yet to find much commentary on the resistor connection.
Here is a link to the site, the person who did the MOSFET control who wrote the article is no fool, but I didn't see any comments about the voltage divider.
There is also an interesting question about the 1N4007 diode. For PWM I use a frequency of 50000 Hz (50 kHz) on one of the forums found a comment like - "this diode is too slow for PWM".
On other forums they say to put ordinary rectifier 1N4001.
I having 1N4007 relative 01 of 1N400X series decided to take it.
Have I committed a crime by choosing a similar 07?
And how to determine whether my diode is suitable for 50 kHz PWM?
Unfortunately most sites copy other sites, with all the mistakes.
The 10k resistor has no function for the mosfet. It keeps the Arduino pin at ground potential while the Arduino is still booting, during which the pin is still a 'floating' input. For that it doesn't make a difference if the 10k is on the Arduino side or the mosfet side. But for gate drive it does (a bit).
Did you read the link I gave you?
None of them need a potentially problematic 50kHz PWM signal.
If... a default 1kHz PWM frequency can't be tolerated, maybe because of the slight buzzing noise, then you might consider going as high as 25kHz. Note that some devices, like solenoids, might not like that. Schottky diodes are commonly used for high frequency stuff, or fast recovery diodes.
A 1N5819 is a common 1A Schottky.
Leo..
PWM is needed for the peristaltic pump, it consumes 140mA.
LarryD
Unfortunately, in my country such shops just don't exist. But these things are interesting.
Wawa
Of course, I have familiarised myself with the information in the link.
As for the diode, if you can, please show me where exactly in the specification you can find out at what frequency the diode can operate?
Reverse recovery time is the time the diode still conducts when it shouldn't.
Google "1N4004 reverse recovery time".
Then do the same for the 1N5819.
Leo..
Hello. I chose a frequency of 50 kHz because I saw somewhere that it is better to use a frequency higher than 30 kHz in the hope of smoother operation of the peristaltic pump.
But now I realise that you are right, the frequency is too high and it will only complicate the design. At 25 kHz everything works fine, I will work at that frequency.
According to the specs I found, the diode should be able to handle that frequency, which means I won't have to change the 1N4007. Do you have any other comments on the elements?
What frequency would that be.
A PWM signal is not a sine wave. It's a square wave with rise/fall times into the tens of Mhz.
You will know if the diode can't cope with PWM. It will get hot.
Still remember that I tried to rectify a 15.625Hz pulse from the flyback transformer of a TV with a common rectifier diode about 50+ years ago. Took me a while to realise that the diode got hot from the switch frequency, not the current.
Leo..
