I presume by context you mean the 3V3 power rail pins (pin 1 and pin 17). They are NOT GPIO.
On the recent Pi models you can draw about an amp from the 3V3 power rail. On the earlier Pi models you can draw about 100 milliamps.
As an aside you can only safely draw about 20 milliamps from a single GPIO and about 50 milliamps in total from the GPIO.
You will not find a specification, because there isn't one.
The Pi4 has the same power manager as the Pi3B+ and Pi3A+ so the current limitation would be the same. The Pi3 regulator is rated at 1A and has been tested at 800mA (on 3.3V).
There is no polyfuse or limitation on 5V, so you could in principle draw up to the limit of the power supply, but this ...
Before using a cable you must first notice these things first:
1. Never use a very long wired USB type-c cable
2. E marked or not you should use a cable that can sustain fast-charge
3. Always go for a good quality cable otherwise there will be losses in cable
4. Use a fresh set of cable and avoid using converters.
Use an adapter with minimum 5V-2A. You must ...
First of all I have to say about battery. Battery store energy as voltage. The term of current comes when we are trying to put a load across it. The voltage reduces in a rechargeable battery after using it for a while. A dead battery has no voltage,neither it can provide any flow of electricity.
If a battery dies, and that battery has some abnormal ...
What happens during a brownout is not "physical damage" in itself, rather, digital devices start to behave erratically when underpowered. This can indeed result in physical damage too: if the SoC accidentally reconfigures an input pin as output, it can create an internal short circuit and fry the pin, the SoC itself, or an external device connected to that ...
I did the exact same thing: Shortened the 5V and 3V3 rail by accident (with a probe).
In my case it was sufficient to replace the Power-Management-Chip, which is indeed available. I used aliexpress to order it (MXL7704-R3).
You will however need a hot air rework station. A cheap one as in my case will do, but a simple hot air blower from the hardware ...
The way I see it, no matter what, you will need to issue a poweroff at the raspberry after you do what ever you want to do. At this point you are left with a raspberry that needs either a plug/unplug of the usb cable or grounding pin 5 (or connect pins 5 and 6, 6 being the GND).
So yes, you will need another "brain" that draws a few mA of power and will ...
Here is what you can do.
An electronic circuit may have the tendency of pulling more current than it needs. So if you are using any kinds of power supply through USB make sure you are using a good quality power supply. If possible isolate the power of that hard disk.
The following two configurations work only one at a time:
(1) L298N Driver 1 (D1) works with motor pair (M1a + M1b).
(2) Similarly, D2 works with M2a + M2b.
There are a couple of possibilities, including:
(a) Motor power too weak. The 5V power from Rpi4B's 40 pin connector
(pins 2, 4) might have a problem driving 4 motors. ...
What you have shown is NOT a "schematic", it is a layout diagram, but is too vague to determine exactly what you have (although we can guess), but seems unnecessarily complex.
RPi_GPIO_Interface_Circuits shows output circuits which should work for your small motors. (The Driving a relay is most appropriate).
If using a single transistor you should use a ...
I am using two transistors to drive two fans. Is the following
(1) Ib = 3V / 300R = 3000 / 300 mA ~= 10 mA.
(2) Transistor current amplification factor (h(fe)) > 100.
(3) Ic = Ib x 100 = 10mA x 100 = 1000 mA.
(4) Motor resistance would limit Ic to << 1000 mA, possibly ...
Barring motorbikes, bicycles, and antique cars with manual cranks (of which the last two types don't have CAN buses), every "vehicle" has a battery, either as a primary source of energy, or as a source for combustion engine starter. All you have to do is find a way to connect your data logger directly to the battery, not to a secondary circuit which is ...
Outside of adding hardware to clean shutdown the system when the vehicle is turned off. One option is to mount the usb using the sync option of the mount command. From the manpage for mount:
All I/O to the filesystem should be done synchronously. In case of media with limited number of write cycles (e.g. some flash drives) "sync" may cause life-...
Well, I found the answer to what part is this by writing the Raspberry PI Foundation. The part number is Bourns SRN2512-R47M - Fixed Inductor 470 nH 4.4A 32 MOHM. I can get it for 31 cents but I figure wrapping about 7 turns of 22 gauge wire around a 5/16" drill for 1/4 inch coil length will work the same.
I asked around and it seems that Broadcomm is very ...
Same problem here. A Pi4 will not reboot if a powered USB 3.0 hub with HDD is connected.
I have opened up a cheap Chinese USB 3.0 hub, and de-soldered the red 5V power cable to the computer, so, this one will always need external power to work, and it does. But the Pi4 will not reboot while it is connected. This indicates that the problem is not back ...