How does a diode work?

[zappy]

I was hooking up a doorbell button, and it had a diode in the back. So you had to have it touching both screws on the back, and it had to be on the correct polarity.

So I pushed the button and if you didn't hold the button down, it wouldn't go thru the whole tune.

So I flipped the diode around, and pushed the button and it would go thru the whole tune without having to hold the button down.

Just curious how it works. Thank you for your help.

 

[mike107]

A diode only allows current to flow one way. By holding the button down you probably bypassed it.

 

[__dan]

diode

diode

from your description I have no idea how the diode was employed in the circuit, but you asked how the diode works.

The diode is a junction of P and N type semiconductors. The semiconductors are doped, impurities added, so that the charge carriers are either electrons, N type, or "holes", P type, places in the valence shell for the electron to fall into.

At the PN junction, charge carriers are pulled away from the junction by the formation of a reverse bias voltage, the junction becomes depleted of charge carriers and has a natural reverse voltage bias. If a reverse bias voltage is applied externally, the depletion region is expanded, no conduction and no charge carrier movement occurs.

If a forward voltage is applied, charge carriers overcome the forward voltage drop across the junction (~ 0.7 volt) and the diode is conductive across the junction, less 0.7 volts.

Don't know if that is what you asked for, the diode is conductive for forward voltage bias and nonconductive in the reverse voltage bias.

 

[cadpoint]

You should use your favorite search engine and ask for Diagram a diode enlarge the cherry one (the 6th one) and note that its emits lights from one direction, thus the basic part of your question. Or in fact you only had it installed to touch once those particle sound. But, when you correctly installed it the power hit the diode as designed and let the full power through. The 7th example is almost correct (the top of the diagram is very similar but close to you application), of a touch and energizing application, light. bell(the coil), etc.

The key application is that A diode is one direction, it's design is to let it go (the power) in one direction, that's the key to it's design and application.

I forgot the Current part as posted in the 2nd thread.

OH Sorry that is also page two of the "Diagrams"

 

[mxslick]

Dan gave the best answer, though rich in technical detail.

In simpler terms, think of a diode as the electrical equivalent of a water check valve, permitting flow in one direction only.

As for the doorbell, what's going on is the diode provides a steady DC voltage bias to the bell's electronics which is what allows the notes to continue playing after the button is released.

As for the start of the notes, pushing the button bypasses the diode and puts AC onto the doorbell's circuit which senses the AC and starts the notes playing.

 

[dicklaxt]

There are many configurations of door bells,buzzers,chimes etc the one you are describing above could be this one I will describe and this little blurb will give you a basic on how the diode it selfs works.

Normally door bells and chimes are low voltage rectified AC(pulsating DC) and there is a transformer somewhere that has a 120VAC primary and a 3 to 24VAC secondary,,,,,, the diode,PB, chime load and one secondary output terminal of the transformer are all in series ,the other side of the chime load terminal will go back to the transformer.A diode in allowing current flow in one direction clips off the negative side of the sinewave giving you a pulsating DC voltage output.

Door bell system you describe is probably mounting the diode on the back of the PB for ease of mainteneance and wiring,the pulsating DC is more than likely triggering an electronic card circuit internal to the chime or music box and it goes thru its routine and times out and resets itself.

If this is a LED(light emitting diode) that illuminates the PB then there will be a resistor in series with the diode, wiring connections and schematics will vary widely,could you post a copy of the connection diagram and components in the circuit itself?

dick

 

[hurk27]

The Diode across the push button, in the case of an electronic door bell chime is to provide a DC current to power the electronics, that is all, they make these door bell kits as a replacement for existing system, and since there would be no power for the electronics to allow for the chimes to go through the whole melody once the button is released, they use the diode to supply this power, remember it only conducts in one direction so this means the RMS voltage will be about half of the transformer voltage, so when a person pushes the button a voltage detection circuit within the chime triggers the electronics to play the set tune, releasing the button the diode keeps it playing till the end, without this diode in the correct polarity the electronic would just stop when the button is released since it would get no power from the transformer. there are other diodes withing the input circuit of the chime electronics to also rectify the AC from the transformer, other wise the AC would just burn up the electronics, this is also why reversing the diode does not harm the electronics like it would in normal DC powered equipment.
also some of these units can take batteries, which will allow the chime to work without the diode.

 

[hurk27]

I guess I should sum it up by saying that in this circuit the diode allows the electronics to receive power and also still be triggered from an existing button without rewiring an existing system or changing they way you would wire a door bell, and you only need one diode no matter how many buttons you have.

 

[hardworkingstiff]

So I flipped the diode around, and pushed the button and it would go thru the whole tune without having to hold the button down.

Do you think you would have had the same results if you switched the wires on the PB instead of flipping the diode?

Did the schematic specify transformer feed to a certain screw and chime to the other screw? I'm assuming you had a 2-wire push button.

 

[LarryFine]

Do you think you would have had the same results if you switched the wires on the PB instead of flipping the diode?

What matters is the relative polarity of the diode and the chime terminals.

It seems the diode could be placed at the chime as well as at the button.

Without the diode, the chime receives no power when no buttons are being pressed.

 

[dicklaxt]

Here is a typical door bell power supply you can put the PB anywhere in series with the diode,the capacitor is to smooth out the ripples of the pulsating DC and could be located on the chime/doorbell electronic card,the load in this schematic is the door chime/bell.

I made a 12 volt DC power supply for bench testing circuits and temp power for small projects using exactly this schematic about 40 years ago and it still is working fine.

The diode in this case allows current to flow thru the diode when the switch is closed,when the current changes direction it is blocked so theoretically it is a pulsating DC and not a true DC as there are highs and lows on the positive side of the sinewave,more capacitors could be added to further smooth out the ripple and an additional diode could be added to make it a full wave rectifier.This diode would funtion on the negative side of the sinewave allowing current to flow and at the same time flip the bottom V max from below the line to the upper side of the sine wave giving you twice as many peaks on the wave which would further smooth out the ripples.

This type power supply is often used in low V/I(voltage/current),larger power supplies using 3 phase power and heat synced power diodes is also used,there are many applications.

dick