A couple of somewhat basic questions.

[Iskuri]

Hi there, I'm very new to electronics, and to this forum, and just had a couple of questions relating to a few projects I am working on. In general I work with my arduino for projects, everything going through it for a few basic things, but lately I have had a couple of ideas relating to lower power circuits (not using an arduino). So here are the questions, hopefully the nice people on this forum can help!

My first question is: How does one wire up a capacitor in a circuit in order to discharge its charge when it has gathered enough power? (this may be an impossible feat, I am going on an assumption, not 100% sure of how capacitors work if I am honest). Basically I have something with an incredibly small power output that I wish to build up in the capacitor and then discharge at a certain level of charge. Can this be done by the capacitor being wired in series with the power supply?

Secondly, how does one calculate the potential power storage capabilities of a capacitor, voltage and amperes, once again this may be a completely stupid question.

My final questioin pertains to crystal radios. I know that these devices play radio through a crystal earpiece with an extremely high impedance and require no method of amplification. My question is: what is the best way of amplifying the sound with a small battery to increase the power? (A circuit diagram of an amplifier would help me greatly)

Thanks a lot for reading my thread, and sorry for the possibly completely noobish questions! Stick with me and I might improve ha ha. I don't want my hand held with these things but a nudge in the right direction would be greatly appreciated.

 

[(*steve*)]

The first question is difficult to answer. I'm not sure what you're trying to do.

The answer to the second question can be found here. It's 1/2 CV^2 Joules.

The third question can be obtained by googling "crystal radio amplifier". This was the first hit I got and it has several examples. Note that you can look at both audio amplifiers and RF amplifiers (an interesting subset of which is regenerative amplification). There is no reason why you can't use both.

 

[Iskuri]

Thanks a lot for the answers, they've been really helpful. What I meant by my first question was basically: how do I create a circuit that discharges a certain amount of volts into an led each time the power supply on it charges the component(I believe what I require is a capacitor) to its capacity. It's hard to word what I mean.

 

[kwoolsey94]

to answer your first question you will have to use one of two things. Either a switch relay that would have to activated or an omega chip. ( not for sure of witch model.) this would activate with an led telling u to push the switch or the omega discharging.

Finally I have to agree with the previous post.

 

[Iskuri]

Hmm OK I will look into those things. It seems like I have gotten the wrong end of the stick when it comes to capacitors, and more online sources seem to provide poor explanations of what they actually do.

 

[kwoolsey94]

Your best bet is to put a relay on it to where when charged an led will light up and you can manually trip a switch. Thats what i did for my coil gun project.

 

[Iskuri]

Perhaps. Basically what I want to do is have the small voltage power supply charge up whatever component I am thinking of, which from what you have said seems to be a relay, which will then discharge into an led for a flash, and then charge again for another flash, nothing else. Is this possible with a relay? Can relays store charge?

 

[kwoolsey94]

When i use the term relay Im meaning a simple circuit. Lets say you have your Power supply charged. You want to have an led turn on once its reached a certain point of the capacitor. This will then tell you to hit a switch that will release the charge to what ever you want. Thats all I mean by relay.

 

[Iskuri]

OK, well I will look into it. In your example wouldn't it be possible to wire it up so that instead of an led lighting up it just releases the charge? The issue I am dealing with is that I am working with extremely small levels of power, less than is required to make said led shine, and I want it to charge so that the led shines whenever the charge reaches the correct voltage.

 

[kwoolsey94]

Ok I understand now. Thats something above my head then. I assumed you were using enough energy to make the led shine. I understand what your wanting to achieve but i would not know how to do so.

 

[Iskuri]

OK well thanks a lot for the help anyway you've given me a lot of stuff to learn about at the very least. I am sure I can find what I am looking for if I keep researching!

 

[(*steve*)]

Perhaps you need to be more specific about the small voltage that you want to use to make a LED "shine".

Perhaps the answer is to use this voltage to turn on a transistor which allows the LED to turn on (powered from some other power source)

 

[Iskuri]

The idea is to take a several times wound crystal radio style antenna set up and instead of sending the electricity to a crystal earpiece, sending the electrcity to an led instead. Insofar as I can tell, I require a capacitor to be charged up, and then discharge when it reaches a certain level of power, so that the led flashes every time it reaches charge.

 

[davenn]

the real problem with your idea is that there just wouldnt be enough voltage/current to charge up the capacitor, well not within any reasonable time period anyway.
You may wait days or weeks maybe months, if ever, for enough charge to build up.
The received voltages at the antenna is in the order of a few microVolts ( uV ) thats ~ 0.000002 V and you want several volts across the capacitor

cheers
Dave

 

[Iskuri]

Wouldn't that depend entirely on the length of the antenna, and the power requirements of the led? (I was thinking several hundred winds around something) Another couple of questions I had were: is there a way of increasing voltage and reducing ampage? That would make what I am trying to do far easier. Also, is there a better way of providing a small amount of electricity without the use of a battery? (I was thinking of using piezoelectric crystals but for that I would like to know a few things like: is a bigger crystal better than a small one for outputting power when tapped?)

Thanks for the advice.