You have a couple of options to control the backlight display.
use an I2C DAC to control the display current via an LED driver IC.
Use PWM from R-pi to chop the current on and off, again via the LED driver IC.
Split the difference, and use R-pi PWM to make a control voltage for the LED driver.
The first method avoids flicker artifacts, but costs you a DAC. ...
It is possible to do as you want.
Do not use 9V battery to drive your motor! It doesn't provide enough current for motor (unless you driving very small motor).
To communicate between Raspberry and Arduino you may use any:
Add a capacitor close to Arduino board, ideally 2 of caps. One of large capacity (provides some energy ...
I use a 9 volt battery snap connector which connects the battery and barrel jack of the arduino uno(I am assuming that the arduino uno schematic is same as original one) as shown here. Raspberry Pi 3b(original schematic) has a USB type power connector and you cannot use a 9 volt snap connector like arduino. It is better to use a power bank or a wall ...
The threshold for sensing shock is in the ~2mA AC range, so the voltage would depend on how the electrodes are applied. Pulsing current is more likely to produce a sensation than DC.
More here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2763825/
Using about 10k ohms for skin resistance (somewhere between dry and damp), you would need about 20VAC to produce ...
As an aside: you are using a relais module, with optocouplers on its inputs, so your schematics are a bit misleading.
Anyway: the Pi could be doing all sorts of things with its IO pins on start-up, I don't know the Pi well enough to tell you exactly what happens, but high-impedance is the most likely.
You need a pull-up resistor instead of a pull-down ...
If the relay module needs pulling high to turn it off, then you need a pull-up resistor to 3.3V, not a pull-down resistor to GND. I'm not sure what the 1K resistor is for.
On most microprocessors, a GPIO pin can be in one of three states:
Input, high impedance
(Because it's a GPIO pin, not a GPO pin).
On powering up, the safest ...
I've an application for which I use a Meanwell PSD-15B-05 to power a Pi 3B+. I note that the Pi 4 has a 3A supply recommended, which is in line with what the datasheet claims a PSD-15B is good for. I doubt normal use of a Pi would see a continuous 3A draw - it doesn't in my case, but I don't know if one supply would run two Pis..
No affiliation to Meanwell; ...
There are any number of 5V@4A DC-DC converters on the market. I searched for "4a DC DC converter" and there were many possibilities.
You could also use a linear 5V 5A regulator but with a 24V input you'll have to have a heat sink to handle the power dissipated.
While breadboarding is not ideal, I'm not so sure that's the problem.
Look at page 5 of that datasheet : notice the conditions for the output voltage specification:
0.5 A ≤ ILOAD ≤ 3 A
It's fairly common for switching supplies to require some minimum load before they can regulate properly. Otherwise the output voltage drifts up out of specification.
I'm not ...
Wire lengths + breadboard!
If you look at the datasheet, chapter 8.2.1, they show that the input and output caps and the diode should be connected at a single point close to the GND pin of the IC.
Looking at your picture, you are using a GND rail, as well as "long" (non negligible inductance) GND wires everywhere.
I strongly suggest that you try to ...
I want to improve the precision of the draw and I don't know if the problem is a sequential software problem
I suspect you are currently limited by the absolute resolution of one step (1.8 degree). Parallel programming can't fix this. It will however be required later on when you need to calculate a path in advanced from a defined source to follow at a ...
It's hard to tell from the pictures if it is a ducted fan or centrifugal fan with curved fixed blades on the outlet to straighten the flow & convert the rotation of the air into more thrust. All the vacuum cleaners I have seen have centrifugal fans, which will not pump backwards even if the motor is reversed. They will still pump forward, but less ...
It is a CMOS chip with TTL compatible IO levels. It will understand 2V as logic high. Make sure you don't accidentally set the chip to read mode, so that it does not output the 5V supply to the 3.3V IO pins of RasPi.
The normal logic inputs are recognized as a logic 1 if the voltage is above Vih (2.0 volts).
However, CMOS devices often take current from the supply if the input level is not close to the supply rail.
The level at which they specify the standby current when using CMOS level inputs is 100uA(Isb2), but to guarantee that the CE needs to be at Vdd-0.3v.
If you ...
Supercaps seem to be the best option. But you have to give it time to charge, so its best if you add a mosfet/relay which will turn the hard drive on via a signal from the raspberry pi. Also remember to add a diode in series to prevent reverse current.
I would have suggested you other ways but seeing that it is a hard drive motor and any mishap could affect ...
Normally you'd have the positive lead on A (the inner pin) and the negative on C (the outer barrel).
B is used where switching is required, you can leave it open or connect it to C.
In the past, negative was sometimes used for the center pin, but usually it's positive these days. Check your actual requirements. And check the actual footprint-pin mapping and ...
Here is a block diagram of the LM2596HV from this datasheet:
If the switch transistors fail shorted or the adjustment pot is turned too far to the wrong direction the output voltage can be as much as the input voltage (minus a very small drop from L1).
The Absolute Maximum input voltage for the Raspberry Pi 3 (and 4) is 6.0V.
The LiPo cells have a maximum ...
how to access all 256 pins to read and write from/to them simultaneously?
Not at all. Simultaneity requires the same amount of inputs, and you have less.
Normally, you'd just use a parallel-to-serial shift register as input, or a serial-to-parallel shift register as output here, if you need to interact with all pins regularly, instead of just selected ones.
1.) whith positive voltage current will flow through Q2A and as it is a current mirror, it will also open Q2B. Together with the parasitic diode of the mosfet, it will rise the voltage at R24. This will open the mosfet -> normal operation.
In case of under/reverse voltage, the circuit will close the mosfet (current mirror has a high gain, so it will ...
The second solution with lead acid would be the easiest solution, bare in mind that lead acid need to be refreshed after deep discharge, and maintenance charged.
Li-ion need extra care when charging and discharing, at least least dubble protection for OVP and over current i recommended preferable with a hard fuse aswell. Besides the charging circuit. ...
I just need to spin the motor, one direction, for about a second. It is for an automatic food dispenser, so just a burst for a second or so
Unidirectional control of a DC motor is typically accomplished with an N-FET switching the motor's negative power lead, while the positive remains permanently connected to the supply.
Many of the best modern FETs for ...
@mguima has provided a useful link in his answer. BUT do note Chris Stratton's comments also.
Important considerations include:
Any motor tends to make electrical "noise" which a microcontroller is very sensitive to.
Usually the power needs of a motor exceed that which what can sensibly be fed from a Pi header directly.
The servo voltage needs ...