‘Daytime Running Light’ module (DRL) with ATtiny85


Nicu Florica writes:

A reader of my sites and blogs, Mr. Liviu Hinoveanu wanted to replace classical DRL module made with 555 with Attiny85 programmed in Arduino style.
He send me the schematic and PCB designed with Livewire and PCB Wisard software
After I undertand what module must work, I write DRL_ATtiny85.ino sketch.
Mr. Hinoveanu made module and upload sketch in ATiny85 like in article from Programarea unui microcontroler ATTiny85 cu sketch Arduino.

See the full post on his blog, Arduinotehniq.

Check out the video after the break.


DEC PDP 11 / 24 CPU CARD: State of the art design from 1979


DEC PDP 11/24 CPU card teardown from Electronupdate:

This is a cpu card from a class of computers known as mini-computers.
By the late 1970’s DEC was about to be eclipsed by the microcomputer. At the same time this card was in production the 68000 and 8086 16-bit class micro processors were also in the market: their superior cost would soon take much of DEC’s low end market.
The card uses their FONZ-11 LSI chip set. Most interestingly the CPU instructions are micro-coded and placed into separate chips: the instruction set could be expanded at will by adding more “303E”s. Typically this would be for a floating-point instruction set.

More details at Electronupdate blog.

Check out the video after the break.

Automatic fan controller for server racks


Dilshan Jayakody published a new build:

In this post we describe fan controller which we designed for our 9U wall mount server cabinet. This fan controller is designed to drive a 12V DC cooler fan with pre-configured intervals or by monitoring the temperature of the server cabinet.
Core components of this fan controller is CD4060 binary counter, LM35 temperature sensor and LM358 operational amplifier. In this design CD4060 is used as long duration timer and it can configured to trigger cooler fan from 1-minute and up to 4-hour.

See the full post on his blog here.

ESP32 (34) – BLE, raw advertising

In the previous post, you learned how to send BLE advertising packets with the esp32 chip.

To define the content of the packet, you used a struct, of the esp_ble_adv_data_t type:


The struct’s definition is included in the esp_gap_ble_api.h file:


Although there are many fields available, sometimes it is necessary to be able to define the content of the advertising packet arbitrarily. For this reason, the esp-idf framework provides a raw mode.

Instead of defining a struct, you create a byte array and fill it with the entire contents of the packet’s payload:

static uint8_t adv_raw_data[10] = 

then you can use the esp_ble_gap_config_scan_rsp_data_raw() function to pass the array to the driver. You have to specify both the array and its size as parameters:

esp_ble_gap_config_scan_rsp_data_raw(scan_rsp_raw_data, 8);

When using this new function, it also changes the event that the driver passes to your callback function when the configuration is complete. The new event is ESP_GAP_BLE_ADV_DATA_RAW_SET_COMPLETE_EVT. As in the previous example, when this event is triggered you can start the advertising process:


Raw data

For the advertising process to work, the data contained in the array must correspond to a valid payload.

In the blog post about the iBeacons, I’ve already shown you its structure. Let’s briefly review it:


The payload contains one or more AD (advertising data) structures. Each structure is made by 3 fields:

  • an initial byte that represents the length (in bytes) of the structure, excluding itself
  • a byte that represents the type of the data contained in the structure
  • a variable number of bytes which are the actual data

The codes that can be used to define the type of data can be found in the Bluetooth specifications. Depending on the type of data, it is then necessary to apply a particular format to the data that follows. The necessary information is found in the Core Specification Supplement document (available on the Bluetooth.com website).

Let’s see a simple example: the ADType 0x09 represents the complete local name, which is the name of the device. This name must be specified in AD data with simply a sequence of the ASCII codes that correspond to the different letters.

You can use a website to do the conversion:


The payload to transmit this name is therefore:

adv_raw_data[7] = {0x06,0x09,0x4d,0x79,0x42,0x4c,0x45};

The first byte has value 0x06 that is the sum of the name length (5 bytes) and 1 byte for the data type (0x09).


In the following video you can see how I use the raw advertising feature to simulate the advertising packet of my iBeacon and therefore I’m able to activate the relay as in the previous example.

The source code of the program is available in my Github repository.

Negative impedance converters


An article discusses the negative resistance and negative impedance converter from Analog Zoo:

“Negative resistance” may seem like a purely academic concept, but can be easily realized in practice with a handful of common components. By adding a single resistor to a standard non-inverting op amp circuit, we can create a negative impedance converter, which has applications in load cancellation, oscillator circuits, and more.

More details at Analogzoo.com.

Check out the video after the break.

Why electrolytic capacitors are actually kinda shitty


Afroman writes, “Electrolytic capacitors are common, but knowledge of their limitations is uncommon. A demonstration is shown highlighting the difference in performance between electrolytic and ceramic capacitors in power supplies. Other topics discussed in the video: Electrolytic capacitor construction, ceramic capacitors, ESR, ESL, impedance curves, why “0.1uF”, and more.”

Via Afrotechmods.

Check out the video after the break.

Alexa (Echo) with ESP32 and ESP8266 – Voice controlled relay


Rui Santos writes, “In this project, you’re going to learn how to control the ESP8266 or the ESP32 with voice commands using Alexa (Amazon Echo Dot). As an example, we’ll control two 12V lamps connected to a relay module. We’ll also add two 433 MHz RF wall panel switches to physically control the lamps.”

More info at randomnerdtutorials.com.

Check out the video after the break.