1.5V Project: Headphones Amp

1.5V Project: "NightBug"

Led booster with light sensor. Only a 1.5V battery is required. Current  < 10mA.

Homemade watercolor paint receipt

Watercolor receipt

Pigment:  2 teaspoons

Gum arabic: 2 ml

Water distilled (or boiled but cold): 1,5ml (add partly by 1 ml + 0,5 ml)

Glycerin (pharmacy): 1,0 ml (add partly by 0,5 + 0,5 ml + 0,5*)

Process:

- Put pigment into a plastic bag or any container. I used the "Yellow Ochre".

- Add gum arabic, 2ml. Mix the ingredients.
- Add part of water, 1 ml, and mix more.
- Add part of glycerin, 0,5 ml.

- Probably, the mixture will be quite thick, then add part of the water 0,5 ml – mix, and if you need more liquid consistency follow next with the part of glycerin 0,5 ml.

- Test the paint. Put a drop of paint, and stretch over the surface of the palette (but not on the paper). Let it dry for 10 minutes. There is should be barely noticeable shine at an angle on the paint surface. If it is completely matt and the next *0,5ml part of glycerine.

- Fill into a tube or cuvette.

- Left for a night, better two. Use it or fold it into the foil like I did.

Using these portions I made 5 ml of watercolor paint. (for two 2,5ml cuvettes)

How does it work?
Gum arabic – binder, or just glue for pigment. Glycerol molecule holds water thus paint always will be moisture and do not becomes completely dry. Also, glycerin affects the paint flow. 

(*Should try to add an Ox Gall -> flow)

Do not:
- Add too much glycerin. The paint will be too liquid, and not stable in the cuvette. Probably, you don't want to find that the paint has been peeled off and smeared the entire watercolor box.
- Add to less glycerin. The watercolor will not flow and becomes too dry and sharp like acrylic.
- Do not care about too much or less water. Excess water will evaporate. It becomes harder to control the amount of glycerin if there is too much water.

You have made a good paint if:
In cuvettes:
- It dries into solid viscous consistency but does not become completely dry and brittle.

In use:
- It is easy to moisture and picks up with a brush.
- It has a good flow on the paper.
- A dense layer of paint does not crack on the paper.

How to calculate a tube Class A amplifier. Vacuum triode. Part 1

This is a quick instruction on how to calculate an essential triode cascade. It gives you values of Ra, Rc, and Rg. For example, a double triode tube – 6N2P

Using a datasheet for a specific tube, define the nominal (or max, if needed) parameters: 

- The voltage on the plate (anode), Ua

- Anode current, Ia

These parameters are boundaries and two points on the chart of the load line above, see the red line.

6N2P:
Ua = 250V

Ia = 3,2mA

Anode current is a nominal (or max) current that will flow through the tube, and should not be exceeded. When the tube is in the cut-off region state, the internal resistance ri is high and almost all voltage from the power supply will be applied to the tube plate. Thus, the voltage from the power supply should be set close to the nominal anode voltage of the selected tube. If a DC-rectifier provides to high value, it should be reduced using a voltage drop resistor with a capacitor, which simultaneously formed an RC filter.

Ra with ri forms a voltage divider, so in the practice, some amount of voltage will drop on the load Ra resistor if a tube is not in the deep cut-off region.

Ra = Ua/Ia = 250V / 3,2mA = 78K

in the saturation state (tube is ON, the current is flowing)

voltage drop on the Ra:

78k * 3,2mA = 249,6 = 250V that is U, Ua

in the cutoff

voltage drop on the Ra:

78k * 0,25mA = 19,5V

*78k value of anode resistor gives us a non-linear amplifier, the best load for the linear 6n2p amp is 10-20K, see right char.

Operating point

Define the tube operating point on the chart, the operating point will move up and down on the load line. The best places are in the middle of the linear region. An operating point in practice defines an offset voltage on the grid, Ug.

For exp.:

Ug = -0,5V 

look at the branch with the blue lines. Also, it could be 0,5, 0, -0,75 or -1V...

How can we get the offset voltage on the grid? It does an Rc resistor.

Rc = Ug/Ia (op. point) = -0,5V / 1,75mA = 0,29K

Grid leakage resistor

Rg is a grid leakage resistor, which is defined in the datasheet from 100 to 1M.

The grid has a negative charge. The flow of electrons could cause a huge negative voltage potential between grid and cathode, this process will move the operational point (bias) in the cutoff region, so the grid leak resistor is used as discharging path for accumulated electrons.

---

Tube in the cutoff, Ia -> min

ri = Ua - (Ra * Ia) / Ia = 250v - (78k * 0,25mA) / 0,25mA = 922K

Tube in the saturation region, Ia -> max

ri = Ua - (Ra * Ia) / Ia = 250v - (78k * 3,2mA) / 3,2mA = 0,125K

LTspice. How to...

How do I get ground in LTspice?

Add ground – Press “G” or click the ground button and click on the schematic to add a ground. Press “esc” to quit adding grounds. Label a net – Press “F4” or click the add net button. Type the name of the net and click “OK”.

https://eecs.oregonstate.edu/education/docs/tutorials/LTSpiceIntro.pdf
https://www.duncanamps.com/technical/ltspice.html

Symbols & models

You need an ASY file and an INC file which you download and put in the "Special Functions" directory of LTSpice. (you can put them anywhere but this one makes it easy to find them.) c:\Program Files\LTC\LTspiceIV\lib\sym\SpecialFunctions\ To use them, you can choose the diagram from the ASY file by going to the "Special Functions" components. Then you have to include a Spice directive (under "edit" on the main screen for LTSpice). You type .inc name-of-file Or you can just copy the whole contents of the INC file and paste it into the spice directive.

#

OK so you want to install a collection of tube models and their supporting symbols. Note both are provided with no warranty implied or otherwise.

There are two directories you need to locate. LTspice is a 32 bit program and will be installed in program files in xp or Program Files (X86) in Win 7. Locate the LTC folder..

Path to tube symbols is \LTC\LTspiceIV\lib\sym - unzip the tube_sym zip and paste the folder here.

Next step:

Path to tube library is \LTC\LTspiceIV\lib\sub - unzip the tube_lib zip file and paste the file here.

Start LTspice and under the component folder (AND gate on the menu) you will see a folder called 'Tubes' click on this and you will find diode, triode, tetrode, and pentode folders. Click on the folder of your choice and you will get a number of choices. I have lots of triode models and fewer pentodes, tetrodes, and diodes.

https://www.dropbox.com/s/3el2j4zp36lw2fe/tube_lib.zip

https://www.dropbox.com/s/iwa43rup7w16b6y/tubes_sym.zip

STM32CubeIDE autocomplete doesn't work. Solving the problem

 Using Mac or Linux

Assign the hotkeys,

uncheck

or use with the default settings

- Apply settings and reload the CubeIDE

- Use "Shift+Space" for code autocomplete