Search found 38 matches
- Wed Jul 22, 2020 9:23 pm
- Forum: ESP32 Arduino
- Topic: Many ESP32 modules on single wifi access point?
- Replies: 3
- Views: 946
Re: Many ESP32 modules on single wifi access point?
I don't think it is specifically to do with esp32, rather a question of the size of the packets and the rate at which they are being sent. If the interval between each mqtt packet is a decent amount then there should not be a problem in supporting a large number of devices. I have about 35 esp8266 s...
- Wed Jul 22, 2020 9:11 pm
- Forum: Hardware
- Topic: Pick up WiFi noise
- Replies: 3
- Views: 1149
Re: Pick up WiFi noise
White noise at 80 MHz is a meaningless requirement. White noise is a random signal having equal intensity at different frequencies, giving it a constant power spectral density. (Wikipedia) So if it was white then the power density would be the same at 1MHz,10MHz,100MHz etc. If you give some backgrou...
- Tue Jul 07, 2020 8:08 pm
- Forum: ESP32 Arduino
- Topic: How does ESP32 drives OLED 1106
- Replies: 5
- Views: 1064
Re: How does ESP32 drives OLED 1106
These display modules can either be SPI or I2C. It sounds like yours defaults to I2C. I2C connects to the SCK & SDA pins. They should normally have the required I@C pull ups on the display board. DC in I2C is used as an I2C address selector. If it is pulled low then the address should normally be 0x...
- Sat Jun 06, 2020 11:44 am
- Forum: Hardware
- Topic: ESP32 powering a solenoid
- Replies: 12
- Views: 2520
Re: ESP32 powering a solenoid
I think that even for the 2n2222A version it is hard to come up with a worst case design that provides sufficient Ib to saturate and yet doesn't potentially try to draw more than 40mA from a GPIO. 2n2222A max Vbe Sat @ 500mA Ic 2V might be a bit less at 300mA but not actually specified Assume GPIO V...
- Fri Jun 05, 2020 8:43 pm
- Forum: Hardware
- Topic: ESP32 powering a solenoid
- Replies: 12
- Views: 2520
Re: ESP32 powering a solenoid
Just to amplify further why I think trying to exploit potential 40mA capability of a GPIO would be a bad idea. 1 Vbe sat of a 2n2222A could be 2.0V 2 Vo of a GPIO at 40mA could drop to 2.6V 3 So to guarantee 30mA Ib what base resistor would you use? 4. Then under typical conditions where GPIO might ...
- Fri Jun 05, 2020 8:27 pm
- Forum: Hardware
- Topic: ESP32 powering a solenoid
- Replies: 12
- Views: 2520
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: 2520
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: 3801
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: 7086
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: 2938
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.