obvious questions.....

[madmikejt12]

hi, sorry for asking such obvious questions but i dont know the ansers!!! (obviously, i wouldnt be asking otherwise)

1) what is a solenoid
2) what does a diode do
3) what does a transistor do?
4) what does a transductor do?

feel ashamed asking these but my mind is young lol :roll:

 

[JimB]

Please feel free to feel ashamed!
Our friend Google could answer most of these questions, but I am in a good mood tonight, so here goes:

Solenoid, A coil of wire, used to create a magnetic field. As a horrid generalisation a solenoid is a single layer coil where the length is greater than the diameter.
Often the term solenoid is used as a short form of solenoid valve. A valve to switch hydraulics or pneumatics which is electrically operated by passing current through a solenoid.

Diode, a device which passes electrical current in one direction only.
A diode has two connections, an anode and a cathode. Conventional current will pass from anode to cathode, but not from cathode to anode.(PS, to all the argumentative types, I know that electrons flow from -ve to +ve, but most of the time I like to think in terms of conventional current which flows from +ve to -ve).

Transistor, amplifies current. At this time on Friday night, that is all I am saying.

Transductor, looks like the Spanish word for Transducer.

Transducer, something which converts energy from one form to another.
Examples:
Microphone, converts sound energy into electrical energy.
Loudspeaker, converts electrical energy into sound energy.

OK?

JimB

 

[madmikejt12]

yes, thanks verry much, that realy helped
oh, 1 last thing, in school, we are doing a simple circuit (and case) to test a fuse i.e, if the fuse works, the LED will come on, i was wondering, would it be possible to use a relay so if the fuse works a green light comes on and if it doesnt, a red light comes on? or would i need a 555 timer or similar IC (sorry if this sounds stupid, i'm a beginner lol)

Mike

 

[Styx]

try this

 

[Someone Electro]

Yep thins shod work.

This is an prety good use of the didoes forward voltage.

 

[madmikejt12]

ok, thanks JimB, Styx and Someone Electro. you have all been great help

 

[Styx]

Yep thins shod work.

This is an prety good use of the didoes forward voltage.

Yup it is I use a similar cct at work to provide a nice square pulse of current


Using a current source I have an inductor just to help the whole cct out.
I then have 4 diodes in series closing the whole current-loop back to the supply.

In parallel with that I have an IGBT that I PWM - use this to check bandwidth of current sensors (sensor in the collector patch of the IGBT)

 

[Sebi]

In my country the transductor also called as "magnetic amplifier". Many years ago (before the SCR-s and triac-s), this was the "heart" of mains voltage stabilizers. In the TV-sets also often used as E-W corrector.

 

[Nigel Goodwin]

In my country the transductor also called as "magnetic amplifier".

It's the same everywhere, a 'transducer' and a 'transductor' are completely different things - but I agree that he probably meant 'transducer'.

 

[madmikejt12]

hi, thanks again for your replies, yes, i did mean transducer sorry

 

[madmikejt12]

hi, could you explain that circuit please? my sisters friend (an electrician) says he doesnt see it working, but he may be wrond, the diode limits the current to only flowing one way right? doesnt the LED also do this? (only lets current flow one way)
im a little confused about it :s

 

[Nigel Goodwin]

hi, could you explain that circuit please? my sisters friend (an electrician) says he doesnt see it working, but he may be wrond, the diode limits the current to only flowing one way right? doesnt the LED also do this? (only lets current flow one way)
im a little confused about it :s

With apologies to your friend, but electrians know absolutely NOTHING about electronics! - you wouldn't believe the bodge job most of them make attempting to wire aerial systems in new houses!.

The extra diode is there to add an extra 0.7V drop to the red LED, this means that when the green LED lights it prevents the red one lighting as well.

 

[madmikejt12]

ohhh i get it now, thanks he did say he didnt know much about electronics as it was ages since he did it, are there any specs for the diode i need or are they all the same?

 

[Nigel Goodwin]

ohhh i get it now, thanks he did say he didnt know much about electronics as it was ages since he did it, are there any specs for the diode i need or are they all the same?

Just a standard silicon diode, a 1N4001 would be fine, or even a small signal diode like a 1N4148.

 

[madmikejt12]

ok, thanks alot ill let you know if it works and how i get on on friday

 

[Styx]

A diode ONLY conducts in one direction (well their is the avalache case, but thats another story). An LED is just a DIODE that has been "tweaked" to emit light as well as block voltage

So a diode is a perfect silicon component to only allow current to flow in one direction (hence its use in a rectifier).


There is another proporty of a Diode. the forward voltage. When a diode conducts there is a voltage across the diode (it is exponential but for quick cct design assume it is constant).

So when the diode conducts it has 0.7V across it and it is constant (or there abouts).

An LED has a higher volt drop across it, 1.2V is a good rule of thumb as well.


IF you had a battery of 0.5V and put a diode across it, it would not conduct becuase there is not enough voltage to get over its forward-voltage requirement.


So you have a LED in series with a standard DIODE. The total volt-drop across it is 0.7+1.2 ~ 1.9V. So 1.9V needs to be present to allow that branch to conduct (and for the RED-LED to emit light).

In parallel with this Red-LED+DIODE branch is a GREEN-LED+test leads.

With a faulty fuse (ie open cct) the RED-LED+DIODE will conduct.
With a working fuse (ie it is a short-cct) the GREEN-LED will conduct, this will clamp that parallel branch at 1.2V, this is lower then the 1.9V needed to make the RED-LED branch conduct, thus the RED-LED will not light up and only the GREEN.


In thinking abt it you might want to put a momentary switch between the battery and the burn-resistor.


Different LED's/Diodes will have different current capability so be careful.
What LED's you choose (and what current capability) will determine what value of resistor is needed. That resistor has to drop the rest of the battery voltage (say a 9V battery and 1.2V is dropped via the GREEN-LED, then the resistor has to drop 9-1.2 = 7.8V)

another rule of thumb (that I use) is 10mA is a good current for a standard LED. more current the brighter they go

 

[madmikejt12]

With a faulty fuse (ie open cct) the RED-LED+DIODE will conduct.
With a working fuse (ie it is a short-cct) the GREEN-LED will conduct, this will clamp that parallel branch at 1.2V, this is lower then the 1.9V needed to make the RED-LED branch conduct, thus the RED-LED will not light up and only the GREEN.

a genius

thanks, i will put a momentary switch there aswell

 

[madmikejt12]

so, in theorey, if i put anything that uses a current in place of the diode, it will still work.... am i correct?

Mike

 

[Styx]

so, in theorey, if i put anything that uses a current in place of the diode, it will still work.... am i correct?

Mike

What diode, they are all diodes?

if you mean the non-LED, not really you need something there that has a signincant voltage across it (ie a diode with 0.7V) to increase the forward voltage for the path.

IF you put a resistor in its place then there will still be a slicht leackage through that path and the RED-LED will come on slightly - but then we start getting intot he exponential characteristics of diodes

 

[madmikejt12]

yes, i meant the non-LED, ok, thanks for the help. it is realy usefull