More current from 78xx regulators

Yesterday I needed a little more current from a LM7805 series regulator. This was because I had no heat sink available and it was going in thermal shutdown without giving me time to test the application (more on this application on a future post).

I looked for a 2n3055 or 2n2955 to extend the output current, had none! Bad luck! (that I could find anyhow)

Thinking a little bit, I tough in paralleling, found some circuits which didn't appeal to me, so resorted to the datasheet to find the best way.
By the way, used this document for reference: http://www.harrisonelectronics.co.uk/datasheets/78M05.pdf

Here' the resulting circuit (with my adaptation):

I didn't placed the caps, was just a quick test. The resulting quick deployment:

Diodes were 1N4007 but any of one from the 4000 series will do.
It worked fine, anyhow I should place 3 instead of 2 since their still getting hot to fast (heath sink's are on my to do shopping list!..), well it gave me time to test and that is enough.

Another possibility if a 2N3055 or 2N2955 is available (circuit is for 2955):

Have a nice day!

New control and audio boards for the Trevo transceiver.

Decided to place the control board and the audio sub-system on new boards. This way will have a more standard fitting by means of header pins.
In the mean time I added a tone decoder (LM567), and sound card isolation on the audio board. On the control board I added the code for PTT and redesigned the input pins for the band and mode buttons.

I will for sure use almost, if not all, of the Arduino Uno imputs and outputs.

Here's the audio part (top) and the control board (bottom) with the PTT button for testing:

And the underside of the control board with the Uno:

The rotary encoder and the "IF" shit are in place on the board for troubleshooting, will be removed in the end. Still need to connect the output buffers for band-pass filters relay control


Have a nice week!

Weather station with Arduino, DTH11 and MPL3115A2 Barometric pressure sensor

Nothing special here, I had the sensors laying around and a spare box and Arduino nano module so I just "glued" everything together. In the future I will proably put some remote sensors...if I have time and patience for it.

The finished product (with printed paper graphics glued on the plastic panel):

..This type of LCD is not the greatest of all, just used it because bought two out of curiosity, next time will stick with a classic one.


The internals:

..nothing special, there's a small hole near the humidity detector (blue module near the back panel) for faster response to temperature change.

View from the back, power is by USB directly on the Arduino nano module. The back of the Nokia LCD is visible on the back of the front panel:

Part of the code, just for future reference:
 -------------
 #include
#include
// Nokia 5110 libs
#include
#include
// alti/pressure sensor
#include
#include

 // DHT11 sensor
#define DHTPIN A1     // pin analog 1
#define DHTTYPE DHT11   // DHT 11
DHT dht(DHTPIN, DHTTYPE);

const int SENSORADDRESS = 0x60;

Adafruit_PCD8544 display = Adafruit_PCD8544(8, 9, 10, 11, 12); // arduino
Adafruit_MPL3115A2 baro = Adafruit_MPL3115A2();

  // readh dht11 variables
  float hum = dht.readHumidity();
  // Read temperature as Celsius
  float temp = dht.readTemperature();
  // read addfruit variables
  float pascals = baro.getPressure();
  float mb = pascals/100;
  // clear last data on display and display new data
  display.clearDisplay();
  display.print("--------------");
  //display.print("--- Sensor ---");
  display.print("Humi. "); display.print(hum); display.println(" %");
  display.print("Temp. "); display.print(temp); display.println(" C"); // dth not so accurate
  display.print("mB. "); display.println(mb);
  display.print("--------------");
 -------------



Have a nice week!

Airband receiver kit + Si5351

Got one airband receiver kit from a popular an auction site,

(kit's are cheaper now from what I've seen)


Kit includes everything and even some extra components (better more than less).
It worked first time after assembly. Already with that in mind (or as standalone in case of failure) decided to convert it to use the Si5351 clock generator IC, re-using the airband VFO box I made to convert the PAE receiver from single channel to VFO. The Park Air Electronics receiver conversion wasn't successful because of the low range of the internal VFO without manually retuning the coil so the box and the inner Arduino was kind of redundant:

The PAE airband receiver, single channel selection by dip switch's. for what the air band vfo box project was initial intended:

The airband VFO box was supposed to remotely change the DIP switch settings of the PLL, it worked as I programmed but the VFO tuning range was short so I only got 2Mhz excursion from the main frequency before the PLL unlocking... it was kid of bitter taste of a failure in the middle of a success.

So for the Airband kit I place the Si5351 (and the kit itself) inside the airband vfo box and changed the code from the DIP connections to the clock programming of the Si5351. The connection to the airband receiver kit mixer from the Si5351 is strait forward and worked first time:

For the in place kit connection on the PCB what needs to be changed is the connection to NE602 on pin 6 and pin 7, applying the VFO signal on pin 6 of the NE602, the oscillator part (in the kit) is removed by means of disconnecting pin 6 and 7 to the main board..

..using a simple adapter to be inserted inline without modifications on the PCB :

you see the two "missing" pins on the underside that will no connect pin 6 and 7 of the NE602 to the kit PCB

They are never the less connected on the top part of the adapter board and connected then to the VFO (si5351)


The kit without adapter

Final product with adapter in place and connected to the Si5351:

From left to right, back panel, airband kit, arduino and the si5351 module on top, and on the right the from panel with the LCD display and frequency selection buttons.

Still no external squelch and volume on the box (mid and right pot's) because I don't have a drill around....

The power will be provided from the Park Air electronics receiver, that will remain single channel, so when I power it on will get that channel and another one I can select on the new airband kit.

add:
Here's the schematic for the push buttons by popular request:

I had some email requests for the code, placing here a small example for testing single frequency (change for the interest frequency for the Si5351 to generate)








Have a nice week!

Most import project so far - Night Light

....Yes, if you show LED's to a 5 year old they will never let you go... and if you show that they light up when connected to a battery...you will spend the rest of the day watching batteries getting drained.... If besides all this you have a spare project box in hand the litle ones will find a way of re purposing it!
That's what happened when I showed LED's (she discovered then in fact) to my little child, after playing a bit with the LED's she asked me for a night light, she never had one but she knewed what it was... here's the result:

Her design for the LED placement:

And switching bettwen the J of Joana:

And the heart:

Inside looks:
 

 ... she was also fun of the breadboard....and yellow wires!


I suggested blinking and doing circles using an Arduino but no, it was OK like this...an Arduino was spared!

Have a nice week!

P.S. Now I have to connect to an external supply as requested/ordered!...

FT-707 repair (11) un-converting from CB to 10m

One of the FT-707's that I aquired recently had the CB conversion on band 10A to 10D, that is the allowed CB band in most countries and also the pirates low's and highs spread accross the 10A to 10D band switch.

The hardest part here was finding the right Crystals, the few that Yaesu dealers still have in stock are extremaly expensive.

I had sorted that a regular 14.318 computer crystal would work on the 10m B position (oscillating at 42 .954), very near the 42.987 as standard on the radio.

Here's the local oscillator table for 10m

Now I acquired some less expensive crystals very near the factory frequency and can get coverage from 27.9Mhz to 30Mhz (less 79Khz in the end) on the four segments covering all the 10m band plan.

Low part on the 10A position:

High part on the 10D:

Now it's a true amateur radio, not a CB one.

Since the pin's on the new crystals were larger than the existing ones I made some terminal adaptation, that's why they are higher than the one in the 10mB place, second from the left.

I needed to put new coils (new cores and rewound) for 10mA and B, due to previous expert that touched the radio, that was covered in a previous post.

Crystals used were these ones:


10m A - 42.444 Mhz
10m B - 14.318 Mhz (on the overtone)
10m C - 43.444 Mhz
10m D - 43.888 Mhz

Have a nice week!

"New" equipment - Yaesu YR-901, YK-901 and Heathkit SB-610

..New as in new for me. Last August I bough this pieces of "furniture" for the shack, I know the post is a bit late, it's already October.
Only bough them because it was relatively inexpensive, so worst case scenario (they don't work) the box's will be used for some other project, I didn't tested yet, the decoder YR-901 looks ok, the SB-610 has some changes on the CRT tube connections so will be tested first with a bulb inline and after a small revision.
Here's some images for your viewing pleasure.

YR-901 CW/RTTY decoder:

With the matching keyboard, YK-901:

SB-610 Oscilloscope, transmitter monitor:

The YR-901 decoder will be a nice addition to the FT-102 Line:

...Have a nice weekend!