Mailbag_09aug2020

 Some days ago i received some interesting items from Aliexpress / China. Time for another mailbag blog post!

UV detection card

I did see this item in a YouTube video. It is a cheap card an can be used to detect UV light. I did not yet test it, however it seems useful to have for my experiments with UV leds and lamps and other experiments with optics, The mall picture show the backside of this card.

Digital test pen

On Aliexpress i found this cheap digital signal test-pen to test 5 and 3 volt digital signals.  I hope to post soon on my blog some hacks/little improvements.

Pen with conductive ink

In several articles and YouTube videos people experiments with electrical conductive ink are presented.
It looks that you can easy draw your electronic circuit on paper and glue with conductive glue your components. I found this conductive ink on Aliexpress and decided to give it a try.

I did not yet full tested the product. Perhaps i did buy a to cheap conductive ink pen as it was more difficult than expected. Before the ink started flowing i had to shake the pen and to move the pen over the paper several times. When shaping the pen you hear a little ball (?) moving in the ink reservoir.

After trying to write suddenly ink starts to come out of the pen. With my multi-meter i measured the resistance and it was not conductive. To get a conductive line i had to write the same line several times and dry the ink with my heater that i normally use for heat-shrink tube. (First I did not yet use it for real electronic experiments.

Lamp holder

This are cheap lamp holders for GU10 lamps. I ordered some as i want to replace some halogen lamps with GU10 led lamps. At the local hardware stores (Praxis or Gamma) i could not find lamp withe the same diameter as the current halogen lamps.

Temperature sensors

These three legged items perhaps look as transistor. However they are cheap smart temperature sensors (DS18B20 ) .Two wires are for the plus (+) and minus (-) and one wire is used for data transmission to a micro-controller.  Several of these sensors can be placed in parallel and the temperature of each sensor can be read individual as all sensor have an unique address.

Hand drill

This little tool is something i should have bought sooner. In the few days i have it now i used it several times. It has a little drill chuck for little drills. This way i can easy make little holes e.g. in plastic and do not need to use a fast rotating electrical dill or Dremel or punch a holes with other tools.

LCD

Received two LCD displays from China.
Plan is to use them with my FPGA('s).
Therefore soldered Dupont connector pins (See pictures below).
Expect that for playing with these displays and posting something about it will take more time than the soldering....

LCD 1602

LCD 12864

USB Microscope NeoPixel picture

Some pictures of a neopixel taken with my USB Microscope

What is a NeoPixel:

A NeoPixel is a small color led light with 4 connections.

Two points need to be connected to the power ( plus and minus ) One other connection is for an input control signal and the fourth connection may be used as output to connect to the next NeoPixel.

This way a lot con NeoPixels can be connected like a chain. The photos in this post are from a set of pre-soldered neopixels on a pcb where you can break out a small round pcb with one neopixel and the connections. This round led pixels can be used together with a micro controller (arduino, esp, .. ) in projects.

(this picture is NOT from the USB microscope but taken with my smartphone

The first input needs to be connected to a micro controller. The micro controller can send send a signal and control each individual led separate to set the color and brightness.

Microwave Radar Sensor RCWL-0516 -2- (led)

Motion detector with led 
This is the next post on this blog testing the RCWL-0516 sensor. This sensor uses a “microwave Doppler radar” technique to detect moving objects and has a sensitivity range of ~7 meters.
The sensor does NOT detect if someone is near , it can only detect movements!

A long time ago my first post was about using the Microwave Radar Sensor  RCWL-0516 with an Arduino Uno.

 

This cheap and interesting module has the following connections :

• 3V3  - Output 3V3 Regulated DC (100 mA)  This is 3V3 Output NOT input !
• GND - Ground 0 V
• OUT - Microwave Radar sensor output ( HIGH (3.3 V) motion detected/LOW (0 V) idle)
• VIN  - 4 to 28 volt input to power this module
• CDS - This pin can be used to disable detection. You need not to connect it. (Low= Disabled)

A 9 Volt battery was used to power the module. Be aware that after powering the module there is a delay (10 seconds) before the sensor is active.

Besides the CDS pin it is also possible to solder a light detecting resistor ( LDR ) in to the two holes below the RCWL-0516 text/logo. (On the other side of the PCB it is in the top-left square). When there is light on the LDR the Microwave Radar Sensor will not give a signal on the OUT pin.

In this post i describe recent tests using this proximity sensor without a micro controller. The photo's with the Dupont wires on the sensor connectors where from the previous post. This time i soldered pins to a sensor.

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1) In the first test i connected a "standard led" between the OUT and GND with a 220 ohm resistor. This is a simple configuration to test the sensor

2) As i also wanted to check if the circuit is on i also added a (red) led between GND and 3V3 

3) The next idea was using a laser led. The advantage of using a the laser is the very far distance of the laser beam can travel before projecting a dot. The laser light can travel further than standard WiFi, Bluetooth or 433MHz radio signal. On a distance of more than 40 meter you should be able to see if there was movement near the sensor. 

The disadvantage is that you need a line of sight and you can not check if the sensor is functioning as the laser is default off. I tested drivign a cheap laser led directly on the output. However it seemed not possible to drive directly a laser (at least not the small lasers i have) with this module. So direct driving a laser led was a failure. The laser led does light when connected between ground and 3V3 an option could be driving the laser indirect e.g. using a transistor, opto-coupler or relay.

4) I also wanted to do some tests to know if it is better leaving the CDS 'floting' or connect the CDS pin to a logic level.

A prototype perf board was used to create a development/test board for a real test environment. Using wires only would reduce space however it also would lose some flexibility. I did not want to order a PCB or use a breadboard.
Bottom right is the power connection. The switch is used to turn the battery power on/of. Jumpers where used to enable or disable parts of the circuit. I did not want to use a (more expensive) breadboard.
Different colors for the jumpers are used.

The red jumper is used to enable the 'power on' led

The yellow jumper is used to enable the yellow 'signal out' led (using a resistor) 

The white jumper can be used to connect CDS to GND.

Also additional pins an connectors where added to play and do (lateron) more experiments with this sensor.

The sensor pins from left to right (extended over the full lenght of the perfboard) are   

01 - CDS

02 - VIN 

03 - OUT

04 - GND

05 - 3V3  

Results: 

It is possible to direct derive a led with a small resistor) between the output pin and ground without a micro controller.

A battery powered board with a circuit  to test the RCWL-0516 was created and could be used to test the sensor.

Direct driving a small laser led was not possible. Perhaps indirect using a relay, transistor opto-coupler this is possible.

First test showed that motion at about 3.5 meter could be detected using this circuit.

Currently i can not yet decide if it is better to leave the CDS pin floating or connecting it to a logic signal. Both options seem to work. More tests need to be done to decide what is better. 

Some links about the RCWL-0516 sensor:

• https://www.electroschematics.com/get-started-microwave-radar-motion-sensor/
• https://github.com/jdesbonnet/RCWL-0516

Project 0

Sometimes very small project can be useful. This is one of the smallest projects made with two led preferable with different color.

Playing with a low current, low current circuit i wanted to add some leds.  To simply check the signals and deciding how to add the leds I soldered two leds in opposite direction. By using two different color leds (red and yellow) immediate see the polarity even from a distance or in the dark during the test phase of the circuit. This as leds are polarity sensitive.

It is possible to add a resistor, however for a temporary test in a low power low current circuit this is not needed. 

Dual frequency RFID reader -2-

To test my dual frequency RFID reader added some Dupont connectors on the other side of the provided cable.
To make easy changes i decided to add one pin connectors to all the wires. All cables have different colors, however i also wanted to put them quick in the same order as on the connector. So i put all the wires in the right order through an 8 pin Dupont housing. The plastic 8 pin housing can be put on any position as it can move free and is only for quick putting the wires in the right order.
(In fact it is a complete Dupont housing, i did cut of a small part of the housing where the holes for the wires are smaller.)
Hope this little hack will prevent mixing up the wires.
I already did a quick test of the Led with a small 1.5V coin cell. When putting the 1.5V coin cell directly on the leads of the led it lights up. Connecting 1.5V to combinations of wires like VCC (Red),  LED (Orange) and GND (Black) did not light the led.
A next step will be testing the RFID sensors, the led and buzzer. For the final part i need to decide if i will use an Arduino or an ESP module and where exactly i want to place this reader.

Dual frequency RFID reader -1-

For RFID experiments i also have a cheap dual frequency RFID reader with enclosure from my old mailbag. Bottom side of the enclosure is open. The size is about 7,5cm * 11,5 cm. A resin protects the components and a connector with wires (30 cm) is included.
It contains not only a 25Khz and 13.56MHZ  RFID reader. Also a led and buzzer is inside this enclosure.
For the RC522 RDIF reader there are several examples on the internet. For this reader i did not yet find much instructions. Also i and did not yet test the module.

Website of manufacturer ( Chinese)
https://gwiot.com/

Website with use example (Only RFID not using buzzer or led test)
https://smartpoker.jimdofree.com/modules-rfid/lecteur-rfid-7304d2/
The page contains links for code and more info to

• https://codebender.cc/sketch:26510#RFID%20Wiegand%20Example.ino
• https://github.com/nlamprian/RFID

Additional info on this page
https://world.taobao.com/item/45234761820.htm
Google translation of some text on this page about temperature sensibility
Special Note
     1. If the product with a temperature resistance of 60 degrees is placed in the gate, the direct sunlight at noon in summer will seriously affect the IC card reading function. The product with a temperature resistance of 80 degrees can work stably.
     2. The sensitivity of card swiping of temperature-resistant 80-degree products is higher than that of 60-degree products.
     3. It is recommended to use the pedestrian gate only, which has good adaptability to the metal environment.
    4. The default stock color of the product is carbon black. If you need white, please communicate with customer service if there is stock.
  5. The temperature-resistant 60-degree dual-frequency read head has been discontinued and needs to be ordered.
Due to the (poor translated) text above i expect better to keep the module out of direct sunlight if possible.

According the internet the following cards can be used:

13.56MHZ /  ISO14443 TYPE A	NXP_Mifare1k NXP_Mifare4k NXP_Mifare mini Ultralight (C) Mifare  PlusX(S) Desfire  D21  D41  D81  NTAG203(F)
125KHZ	EM4100 EM4200 JT120 (??)

A Chinese mini manual was included when delivered from AliExpress. In this first post about this module only some info, pictures and a first try to translate the manual using google translate. Hope it will be soon possible to make a next post about this module with some results.

COVID-19 data -5-

Short post on my blog to share a link to Github files containing Dutch Covid-19 data.
Not tested  / full checked however looks reliable and up to date ( 7/7/2020)

https://github.com/J535D165/CoronaWatchNL
COVID-19 disease count cases in The Netherlands by RIVM, LCPS and NICE