Hardware review for sailboat autopilot

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1

Hello everyone,

I am working on a personal project to build an autopilot for a sailboat using an ESP32, and I would like experienced people to review my schematic to check if I haven’t missed anything and to give me advice on what could be improved.

Power Supply: For the power supply, I am using two linear regulators to output 3.3V to power the ESP32 and most of the board, as well as the 1.8V required for the direction compass. I’ve included a MOSFET for protection against polarity reversal and indicator LEDs that light up when the power is nominal.

Alimentation
Alimentation1169×827 39.3 KB

ESP32 Section: For the ESP32 section, I’ve included the minimum required components to be able to program the ESP32 via an external FTDI USB. Could you please verify that I haven’t missed anything (there are schematics all over the internet, and they all seem to differ)?

Esp32
Esp321169×827 66.2 KB

2

Thaks a lot for your advices and time.

3

That is not a power supply. Are you going to leave the sailboat connected to shore power?

4

No but the pilot will be connected to the battery pack off the sailboat.

5

Aside from the fact that you probably meant "autopilot" It's customary to include the battery voltage range in your documentation.

Or maybe your pilot is an android. :grinning:

6

Sorry english is not my mother tongue.

Yeah the autopilot will run on battery pack (standard AGM between 14.5v and 10.5v).

1 Like
7

  • Your LED resistors are too low.

  • Always use de-coupling on digital power pins.

  • Suggest you add EN(Reset) and Boot switches to your ESP32.

8

What do you predict your current consumption to be on the 3V3 supply? your linear regulator will dissipate 11 W at maximum battery voltage and 1 A current consumption. That's a lot of power for that package even if you've provided a heat sink.

9

Your LED resistors are too low.

Can you help me on how to calculate them please ? (I calibrate the resistor for the current on the Led based on the datasheet).

Always use de-coupling on digital power pins.

Do I need to add decoupling even if I had decoupling on linear transformer output ? How to know the rating off the capacitor. Can I add 1uf ?

10

Keep in mind that every time you change a voltage you are wasting the power being supplied by the battery. The linear regulators are the very worst wasters of power. Try to make all devices use a single voltage, preferably the highest possible. Then only a single voltage reduction is necessary. The higher the voltage, the smaller the wire size for distribution.

11

I predict 500ma tops maybe 1A for peaks (for esp32 at boot time for a few ms).

12

Thanks for the advice.
I choose linear regulator to reduce the EMI because the autopilot use a compass who will be on the same pcb.

Unfortunately, i can't find a compass who run on 3.3v and meet my requirement.

13

Sorry, I did not understand you were that far along with the project. Are you sure there is an EMI problem?

14

Update part with your first advice. And adding 10uf decoupling on power line near the components.

schematics below

Compas
Compas1169×828 40.8 KB

Pont en H
Pont en H1169×827 33 KB

Esp32
Esp321169×827 67.3 KB

15

Alimentation
Alimentation1169×827 39.3 KB

16

So, that means around 5 W normal operation. The TO-252 package you indicate you have chosen has a chip junction to case thermal resistance of 12 W/ºC so that's 60ºC temperature rise to the package surface. The data sheet doesn't specify the case to air thermal resistance but that will add to the chip temperature and doesn't help. I would strongly suggest you reduce the input Vcc to the regulator with a buck regulator that you can locate away from your circuit if EMI is a problem.

17

I already have encountered problem with EMI using this type off compass.

I have choose to go with linear regulator to get rid off that problem from start.

18

Thanks for the advice I will do that, is this ok if I reduce to 10v input. The h bridge need to power a motor who run from 9v to 20v.

I have a place for a thermal dissipator if needed.

Just a question, can I put two linear regulators in // to split the load and the temperature rise ?

19

That will help. Since the factory data sheet for your regulator is not complete a suitable test might just be holding your finger on the chip when it is supplying the required current. You could add an additional linear regulator to reduce the input to your 3V3 regulator and retain the full battery voltage for the motor as well as solving your suspected EMI problem.

Edit: I just saw that you asked about that. the answer is yes.

20
  • Let’s see if you can . . .

What is the LED forward voltage drop when ON ?
What is voltage that powers the LED ?
What is the LED current through the LED when ON ?

  • Typically a 100nF (.1uF) ceramic capacitor is used.
    Place this capacitor as close to the power pin as possible.
    An SMD 1203 or 0805 package is commonly used.