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This type of amplifier is called a “Common Emitter Amplifier” Note that this amplifier won’t give you a lot of current like a real function generator

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What you need

• A soldering iron
• 2.2k resistor(Optional power led resistor)
• a LED or more(if you want lighted Cigrette lighted sockets)
• A Resistor that is $$\frac{12_{V}-(n*V_{F})}{I_{F}}$$ Where Vf is the LED Voltage Drop, n is the number of LEDs and If is current usually 20mA
• DC-DC boost converter that outputs the same voltage as your charger but runs on 12vdc
• A spear ac adapter to salvage the connector that fits the computer(I used one from a old motorola cellphone charger adaptor that I got from a hamfest)
• Cigrette ligher cable. Got that from the hamfest as well!
• Female Cigrette lighter connector I got two of them with 3 connectors each for free.
• Heatshrink tubes(Prevents short circuits)

My chromebook uses 19VDC @ 2.31A so I looked at eBay for a boost converter, this is because car voltage is only 12VDC it needs to be stepped up. The chromebook may run from 12VDC directly it probably won’t charge. I got a 3 female Cigarette lighter socket from a hamfest and add 3-green LED in series with a 240-ohm resistors and put them close to the hole in the middle of socket, making the sockets lighted.

Steps

1. Cut the cord with the end that fits the computer. DO NOT CUT IT TOO SHORT BECAUSE WE WILL USE THAT PIECE TO ATTACH THE BOOST CONVERTER TO THE COMPUTER.
2. Use your multimeter to find the wire that goes to the tip(Center usually +) and the sleeve(Usually ground). Solder them to the output of boost converter. You may want to attach it to a insulator on copper tape if your going to add a LED.
3. Connect the LED with the anode(before the arrow on the LED symbol) to resistor and +Vout and cathode(the line, after the arrow symbol) to ground This LED lets you know if its on, wired correctly and has enough juice to power the computer(it will flicker/blink if the computer overloads the boost converter
4. If you want to light up the cigarette lighter female plug just put them close to hole where the center +12v is. You can wire them in series for multiple jacks, like in the circuit below. The formula for the resistor is $$R_{1}=\frac{12-(V_{F}*n)}{I_{F}}$$ where Vf is the forward voltage drop n is the number of LEDs and If is forward current.

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Parts list

1x USB Extension Cord

cheap heatshrink assortment

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What can that do to the circuit?

If you are using a 3-prong chromebook or are hooked up to a 3-prong charger you would have to be extra careful where you connect the ground clip. If wrong BANG you can blow your circuit up, break the probe, blow your hand right off(if enough current),make a big spark.

How can I fix it?

You can cut the RCA adapter cord or get a spare RCA Cord with one end RCA female and the other end male(like an extension cord). and solder the wires opposite.. Where the tip of the RCA on one end goes to the shield and the shield to the tip. The polarity is only wrong for Android and Chromebooks. I choose to use 2 extra RCA cords just because the ones on the adapter is short and also be able to unhook it and use it direct carefully if the extra cord exposes it to RF. I think its already correct for apple devices like iPhones and iPads.

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where C is the hypotenuse in amps I(A) is side a in amps, I(B) is side b in amps

The circuit I made is using PNP Transistors, it can use NPN but the power supply polarity must be reversed. It uses 7 transistors, and most of them they have collector and base tied together. The circles with “A” in it are where you need to measure the current and C is in the center the 200 ohms are current limiting resistors that protect the variable resistors and transistors from drawing too much when set too really low resistance.

The transistor I used was a 2N5401

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TV Arduino Video Poker machine with real poker machine buttons.

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Here’s the schematic of it:

You can see the idea on how this analog computer works, it uses ohms law to get current from resistors in the circuits. Each current is limited in binary. Also parallel resistance makes the current add up. This circuit can make current from 0 to 300 micro amps. This circuit can last for days on batteries. A 8 volt regulator should be used so the voltage stays at 8 volts.

So you might be thinking how can this analog computer add and subtract numbers?

First of all we need to know ohm’s law. Ohm’s law states that if we know 2 out of 3 variables(voltage,current or resistance) we can solve for the variable that we don’t know.

$$R=\frac{V}{I}$$

$$I=\frac{V}{R}$$

$$V=IR$$

V is input voltage I is current and R is resistance

So if we want 80 micro amps and our input voltage is 8v

$$R=\frac{8}{0.00008}=100k$$

Now the next thing is to know series and parallel resistance.

When resistors are in series the current lowers and resistance adds up.

$$R=R_{1}+R_{2}+R_{3}$$

in parallel the currents add up resistance goes down.

$$R=\frac{1}{\frac{1}{R_{1}}+\frac{1}{R_{2}}+\frac{1}{R_{3}}}$$

Next we calculate the resistance that is needed to generate 10,20,40 and 80 micro amps

$$R=\frac{8}{0.00001}=800k$$

$$R=\frac{8}{0.00002}=400k$$

$$R=\frac{8}{0.00004}=200k$$

$$R=\frac{8}{0.00008}=100k$$

To subtract do the second equation by trying all possible values for A

$$A=B-C$$

$$C=A+B$$

Once I get all of the parts I will update this post

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