school project with capasitor

[ha_jurgen]

Hi.

In our school project we have get this parts:
- Capasitor (10uF ~ 400V) - as the input
- Light bulb - as the output

Capasitor will be fully charged and when you press the switch, capasitor should discharge himself -- "thru some electronics and transformer or coil " -- end this should light the bulb.

Project goal is:
Light a bulb for longest possible time ( till the capasitor fully discharge himself ).

Dumb questions:
- how should i connect this input and output and what should i use between ?
- how long can i light a bulb with this voltage ?
- can someone help me with some basic schematics becuse i have no idea what to use and how to connect (triac , something like tesla coil, normal transformer ? ).

Greetings !

 

[Hermano Canguro]

I dont' think that you could turn on a light with 10uF capacitor, what level of math did you see in your school can you read this?

I =( 400V / R) e^(-t/rc)

suppouse a inital I of 10mA ( you can turn on a led with 10mA)

R = 40Kohms
c = 10uF

I = 10mA ( 1 - e^(-t/0.4))

[/img]

 

[ha_jurgen]

I dont' think that you could turn on a light with 10uF capacitor

There must be a way becuse this is the project we have to do and i can not say " i have no clue how to make this". :|

what level of math did you see in your school, can you read this?

We have this as part of practical exp. an we can use any approach that we want or any math level. The main thing is to make this work.

This is project which was tested before and now we have to make something similar to this.

 

[vortechs2k]

I'm going to assume since you're given a small cap that you're probably using and LED rather than a light bulb. I've illuminated LEDs with as little as 1mA of current, but read the data sheet and try to do some testing with comparable parts to find out the minimum amount of current needed to visibly illuminate that LED. You're also going to want to check the forward voltage drop of the LED you're using and put a resistor in series with it to limit the current and get rid of the excess voltage. To figure the value of the resistor use the equation:
R = (Vcap - Vf)/Imin

Where Vcap is the voltage to which your cap will be charged, Vf is the forward voltage of the LED, and Imin is the minimum current to give visible light out of your LED.

 

[ha_jurgen]

I'm going to assume since you're given a small cap that you're probably using and LED rather than a light bulb.

This is the main problem and this is why i have post this question. Capasitor has only 20uF and expimaent was done end tested before us. So there must be a way to light this bulb.

I this project i can use triac, diac, coils, voltage comparator etc.

This is just my idea:

capasitor -- triac -- connected on primary 12V coil -- discharge --converting high voltage to high power.

 

[Hermano Canguro]

Check your work requirement and post all its

 

[vortechs2k]

This is just my idea:

capasitor -- triac -- connected on primary 12V coil -- discharge --converting high voltage to high power.

you're going to want to limit the number of components you use since you are only given one source, the charged cap, and you don't want to waste too much energy converting it. and i don't see how a triac will help you here.

Just a note: I think your best bet for a first step is to find the minimum voltage/current to turn on this light bulb. Then, you can design a circuit that will keep the current at that minimum for the longest period of time possible while keeping the voltage above the minimum.

 

[ha-jurgen]

and i don't see how a triac will help you here.

Now you will smile, but what a heck . The idea was to discharge this capasitor thru triac on ignition coil. Capasitor current should be enought to start the ignition coil. When the coil starts then i can convert high voltage to high current, needed to light a bulb. I think that this is good idea ....

@Hermano
My work req. is to light a bulb and i can use anything i want , until this is simple and effective ( like eg. before ).

 

[ha-jurgen]

Any idea guys ?

Another idea:
Connecting capasitor to primar side of ignition coil
Switching/breaking the current with transistor

Problems:
I need to set switch between capasitor and primar to stop capasitor to discharge before he is full and i dont have idea how to make transistor part.

Please guys, share some basic schematics / light on this ...

Regards !

 

[docel]

and i don't see how a triac will help you here.

Now you will smile, but what a heck . The idea was to discharge this capasitor thru triac on ignition coil. Capasitor current should be enought to start the ignition coil. When the coil starts then i can convert high voltage to high current, needed to light a bulb. I think that this is good idea ....

@Hermano
My work req. is to light a bulb and i can use anything i want , until this is simple and effective ( like eg. before ).

Sorry guys, but I dont see the "bulb" details anywhere. ie., Voltage or Current rating.

ha-jurgen!
You cannot "When the coil starts then i can convert high voltage to high current, needed to light a bulb"
P=VxI (primary = P=VxI secondary (theoretical)
Practically there is IxIxR losses and the PSec is less than Ppri.
Secondly, as others have tried to explain to you, 10Ufd has very little current capacity. All you can get is a "flash " of light with this capacitor. To see this light you'll have to use a very low current "bulb". Toy cars have these little bulbs 1v/.02A bulbs and may be the best you can do. Even this will be less than a second.

The best bet is a LED. Super Ultra-bright leds will light up quite qell @ 1ma current.

Anything else , (with other components etc.,) will just be a "fun" circuit without any scientific, engineering or electrical basis.

For example: You can use this 10 ufd cap at the base of a transistor and light a bulb for quite some time, depending on the Transistor gain. A darlington transistor with a collector load bulb connected to an EXTERNAL battery or Power source will stay lighted for some seconds.

Now, Thwe best you can do is tell us what components the " someone" who has already made used so that everyone here can guess if it is a "fools Bulb" science fair project (generally used for FUN effect.)

[The capacitor connected to the Ignition Coil primary wont DO anything: The current is too less and the ignition coil needs current in " amperes" to do something]:!: