Search found 43 matches
- Fri Jun 05, 2020 8:27 pm
- Forum: Hardware
- Topic: ESP32 powering a solenoid
- Replies: 12
- Views: 12417
Re: ESP32 powering a solenoid
When using bipolar transistors for switching you do not use the current gain (beta) to determine appropriate base current. That parameter is specified when the transistor is in its linear region with a significant Vce. Gain drops off dramatically as Vce falls. The normal 'rule' for switching is that...
- Thu Jun 04, 2020 8:53 pm
- Forum: Hardware
- Topic: ESP32 powering a solenoid
- Replies: 12
- Views: 12417
Re: ESP32 powering a solenoid
Using a bipolar transistor like a 2n2222 is not a great idea for switching the current to the solenoid. For a 300mA solenoid you would need to feed about 30mA into the base of the transistor to saturate it (switch it hard on). That is to much for a GPIO pin. You could use a darlington transistor lik...
- Sat May 09, 2020 8:52 pm
- Forum: Hardware
- Topic: GPIO drive strength.
- Replies: 6
- Views: 13186
Re: GPIO drive strength.
As has been pointed out a series gate resistor does very little when using a MOSFET driver. The only possible benefit would be to add a degree of protection to the GPIO pin if there was some catastrophic failure in the MOSFET device. These tend to be very reliable devices and I do not add a series r...
- Tue Feb 25, 2020 11:21 am
- Forum: ESP32 Arduino
- Topic: ESP32-CAM Problem with not enough pins
- Replies: 9
- Views: 22831
Re: ESP32-CAM Problem with not enough pins
You can use the TXD and RXD pins as GPIO.
Obviously they are not operational during a flash upload operation which may mean swapping wires to do uploads but if you use OTA then that doesn't matter after the first flash.
Using RXD doesn't affect any serial debug print but using TXD will.
Obviously they are not operational during a flash upload operation which may mean swapping wires to do uploads but if you use OTA then that doesn't matter after the first flash.
Using RXD doesn't affect any serial debug print but using TXD will.
- Mon Feb 17, 2020 8:56 am
- Forum: ESP32 Arduino
- Topic: SAMPLING AUDIO - How to handle large data?
- Replies: 6
- Views: 8443
Re: SAMPLING AUDIO - How to handle large data?
If you use an esp32 module with 4MByte PSRAM (e.g. WROVER) then you can store your whole capture in a buffer before writing out to file.
- Sat Feb 08, 2020 10:57 am
- Forum: ESP32 Arduino
- Topic: Playing gif's with Esp32 & TFT Lcd display
- Replies: 2
- Views: 5589
- Tue Feb 04, 2020 11:55 am
- Forum: ESP32 Arduino
- Topic: ESP32-CAM does not boot with DS18B20 on GPIO14
- Replies: 4
- Views: 6521
Re: ESP32-CAM does not boot with DS18B20 on GPIO14
I don't know why GPIO14 would affect the boot unless it is something to do with the camera software. Maybe try it with a minimal sketch to see if that boots OK with GPIO14 pulled up. On my camera app I do use the SD card so there is little IO free. I use RXD as GPIO3 pin; just use pinMode in setup.....
- Tue Dec 31, 2019 4:01 pm
- Forum: Hardware
- Topic: ESP32-CAM Power Issue - Works with 3.3V but not with 5V
- Replies: 2
- Views: 13320
Re: ESP32-CAM Power Issue - Works with 3.3V but not with 5V
Everything on the board runs from the 3.3V rail. There are 2.8V and 1.2V rails but these are derived from the 3.3V rail. The only thing the 5V connection does is connect to a 1117 linear regulator to provide the 3.3V. So if the board works fine when fed directly from 3.3V then there seems to be only...
- Wed Dec 11, 2019 12:50 pm
- Forum: Hardware
- Topic: Esp32 with LED Strip and chargable battery
- Replies: 8
- Views: 8515
Re: Esp32 with LED Strip and chargable battery
5V power banks contain a LIPO battery, a boost circuit to generate +5V out normally via a USB A socket, and a charger circuit typically with a micro USB input. They are available in various capacities from 2500maH upwards. So you can connect a standard phone type charger into the micro socket for ch...
- Fri Nov 15, 2019 10:09 pm
- Forum: Hardware
- Topic: UART & pins typically used by USB bridge?
- Replies: 2
- Views: 5867
Re: UART & pins typically used by USB bridge?
I don't know about this board but many dev boards put a series resistor between the TX of the bridge and the cpu RX. This allows an external signal to override it without causing a conflict. The TX from the cpu to the RX of the bridge is not a problem. The resistor used can be quite low (e.g. 470 Oh...