Search found 107 matches

by Archibald
Fri Jun 01, 2018 9:57 pm
Forum: General Discussion
Topic: use of LED control for buzzer?
Replies: 12
Views: 5496

Re: use of LED control for buzzer?

mzimmers wrote:-- if I set the timer to 13 bits, and the duty to 0x1fff, shouldn't I expect this to work (at maximum volume)?
To get 50% duty cycle square wave, I would expect to set duty to 50% of 2^13 = 0x1000.
by Archibald
Fri Jun 01, 2018 9:14 pm
Forum: General Discussion
Topic: use of LED control for buzzer?
Replies: 12
Views: 5496

Re: use of LED control for buzzer?

It would help if you provide a link to the type of buzzer you are using. It sounds to me as if it's probably a piezo transducer such as this. If so, drive it directly from a GPIO, not through a transistor.
by Archibald
Fri Jun 01, 2018 7:21 pm
Forum: Hardware
Topic: need recommendation for WiFi antenna
Replies: 8
Views: 4856

Re: need recommendation for WiFi antenna

mzimmers wrote:I've discovered that most of the antennas that meet our size requirements are of very little gain (1-2 dBi) . . . .
ESP32 modules may not have such a good radiation pattern as omnidirectional aerials.
by Archibald
Wed May 30, 2018 11:15 am
Forum: Hardware
Topic: Current Limits
Replies: 8
Views: 15185

Re: Current Limits

Below shows results of measurement of output voltage v. current for drive strength capabilities 0, 1, 2 and 3 (2 is the default). VIgraph.png The measurements were made with the following resistances: infinite, 2kΩ, 1kΩ, 470Ω, 220Ω, 150Ω, 100Ω, 47Ω and 0Ω. But for strengths 2 and 3 the minimum resis...
by Archibald
Tue May 29, 2018 10:09 am
Forum: General Discussion
Topic: What would you like to see in The Next Chip?
Replies: 387
Views: 182579

Re: What would you like to see in The Next Chip?

In my view the main thing that needs sorting out for the next chip is the analogue to digital converter (ADC). The issues with the ADC at present are: 1) Severe non-linearity with 11dB attenuation; 2) With a fixed input voltage, the digital readings vary significantly from one sample to the next (I ...
by Archibald
Sat May 26, 2018 6:18 am
Forum: Hardware
Topic: Current Limits
Replies: 8
Views: 15185

Re: Current Limits

Neither 40mA nor 12mA applies to DAC outputs.
by Archibald
Fri May 25, 2018 9:36 am
Forum: ESP32 Arduino
Topic: Analog inputs from ESP32 more than random generators?
Replies: 3
Views: 5486

Re: Analog inputs from ESP32 more than random generators?

The issue is described here under "Minimising Noise" . . . . http://esp-idf.readthedocs.io/en/latest/api-reference/peripherals/adc.html#adc-api-adc-calibration It is really very poor. The Arduino Atmel processors are very much better. Beware also that I find linearity when the attenuation is set to ...
by Archibald
Thu May 24, 2018 11:30 am
Forum: General Discussion
Topic: i want to map analog pins on 5volt between 0 to 1023 (10 bit resolution)
Replies: 35
Views: 18147

Re: i want to map analog pins on 5volt between 0 to 1023 (10 bit resolution)

Let's consider having calibrated your pH sensor on its own (including the electronic circuit board). If pH=7, the output voltage from the electronics should be 2.0V (ignoring the 'Offset' which should be small). If pH=0, the output voltage should be 0V and if pH=14, the output voltage should be 4.0V...
by Archibald
Wed May 23, 2018 11:52 pm
Forum: ESP-IDF
Topic: ESP32 - I want to decode a Manchester bitstream using I2S
Replies: 2
Views: 1747

Re: ESP32 - I want to decode a Manchester bitstream using I2S

I have received a Manchester bitstream over a very long length of cable so there was significant attenuation and considerable waveform distortion. Due to cable capacitance, the incoming signal looked more like a triangular wave and the amplitude of each peak (positive or negative) depended somewhat ...
by Archibald
Wed May 23, 2018 10:23 am
Forum: General Discussion
Topic: i want to map analog pins on 5volt between 0 to 1023 (10 bit resolution)
Replies: 35
Views: 18147

Re: i want to map analog pins on 5volt between 0 to 1023 (10 bit resolution)

With those resistor values, the formula for pH in your code should now be . . . . pHValue = 4.24*voltage+Offset; My ESP32 ADC functions over the range 0.17V to 3.15V (corresponding to the digital range 0 to 4095). With that voltage divider in place, the range at the input to the voltage divider woul...

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