The post Capacitance substitution board first appeared on Delphijustin industries.

To figure out how long it will take to charge the flashlight you use this equation

$$T=5R_{currentlimit}C$$

And for total discharge time

$$T=5R_{LED}C$$

Where

T is time in seconds

Rcurrentlimit is the power resistor used in charging the capacitors in ohms

RLED is the LED resistor in ohms

C is total capacitance in farads

One thing you should know if the capacitors voltage is lower than the supply voltage you should put capacitors in series to increase the voltage rating on the capacitors. Usually you should use 2 capacitors in series and the supply voltage should be no more than capacitors voltage times 2. The diode will drop the voltage by some and also prevent discharging it threw the wall wart

The post Capacitor powered LED flashlight first appeared on Delphijustin industries.

The following equation is used for figuring out the unknown capacitor(C1) when balanced. I used yacas to rewrite the equation for the other 3 variables.

$$C_{1}=C_{2}\frac{R_{2}}{R_{1}}$$

The equation will show up once MathJax loads

Notes about this project:

• This circuit requires a high impedance headphone(like ones designed for crystal radios) I tried it with headphones and it was quite loud for it to be balanced. I think this was because that it is sensitive to weaker signals.
• The frequency will need to be high, so it will not work with AC Step down transformers.
• This trick probably work best on a oscilloscope. With a oscilloscope you can use frequencies higher than sound frequencies so. Plus at lower capacitance the low current will not throw off the balance point.
• It is probably best ti use a resistor substitution box instead of a pot. This is because with a single turn pot the resistance is hard to find and if the resistance goes below a certain level it can look like you found the correct resistance even when it is not.

With the bridge being balanced you can see it is really close to zero.

Here it is again but this time unbalanced

For this project we will use reference capacitors values 1nF 10nF 100nF and 1µF. R2 should be high as possible.

Capacitor Symbol icon icon by Icons8

program desauty;
uses sysutils;
var c1,c2,r1,r2,cr,rr,ar:extended;
s:string;
label calculate;
begin
	calculate:
	c1:=0;c2:=0;r1:=0;r2:=0;
	write('Enter C1:');
	readln(s);
	if length(s)>0 then c1:=strtofloat(s);
	write('Enter C2:');
	readln(s);
	if length(s)>0 then c2:=strtofloat(s);
	write('Enter R1:');
	readln(s);
	if length(s)>0 then r1:=strtofloat(s);
	write('Enter R2:');
	readln(s);
	if length(s)>0 then r2:=strtofloat(s);
	if c1=0 then c1:=c2*r2/r1;
	if c2=0 then c2:=(c1*r1)/r2;
	if r1=0 then r1:=(c2*r2)/c1;
	if r2=0 then r2:=(c1*r1)/c2;
	cr:=c2/c1;
	rr:=r1/r2;
	ar:=cr-rr;
	Writeln('C1:',floattostr(c1));
	writeln('C2:',floattostr(c2));
	writeln('R1:',floattostr(r1));
	writeln('R2:',floattostr(r2));
	writeln('CRatio:',floattostr(cr));
	writeln('RRatio:',floattostr(rr));
	Writeln('ARatio:',floattostr(ar));
	if abs(ar)<2 then writeln('Balanced')
	else writeln('Unbalanced');
	write('Press enter to calculate again...');
	readln;
	goto calculate;
end.

The post De Sauty’s Bridge first appeared on Delphijustin industries.