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Hi there,
I know nothing about electronics other than it would be a whole lot
cheaper to by 100 transistors rather than 100 DPCO relays...

Could anyone please explain how I could use transistors to
alternatively ligth two LEDs while using a toggle switch with
momentary contacts (normally off)? I would usually use change over
relays but they are expensive and I know that transistors can be used
to drive the DC current used for the LEDs.

Thank you very much,
Marco
PS Ok, I know a little, but just a little.

--- In Electronics_101@..., "scudhome" <scudhome@y...> wrote:

Hi there,
I know nothing about electronics other than it would be a whole lot
cheaper to by 100 transistors rather than 100 DPCO relays...

Could anyone please explain how I could use transistors to
alternatively ligth two LEDs while using a toggle switch with
momentary contacts (normally off)? I would usually use change over
relays but they are expensive and I know that transistors can be used
to drive the DC current used for the LEDs.

Thank you very much,
Marco
PS Ok, I know a little, but just a little.

I don't completely understand what a 'change over relay' is.

can you make a little sketch and post it in the files section of the
website ? please don't attach it as not all of us receive attachments.

In very simple terms a transistor can be used like a switch. you put a
signal onto it, and it passes a larger signal. remove the signal and
the larger signal stops.

if you mean to have a switch to light an LED, why not just use the
switch itself ?

Do you want to push a button to momentarily send a signal and then the
larger signal is sent until the button is pushed a second time...

As you can see, there is a little info lacking to be able to offer advise.

Dave

--- In Electronics_101@..., "Dave Mucha"
<dave_mucha@y...> wrote:

--- In Electronics_101@..., "scudhome" <scudhome@y...>

wrote:

Hi there,
I know nothing about electronics other than it would be a whole

lot

cheaper to by 100 transistors rather than 100 DPCO relays...

Could anyone please explain how I could use transistors to
alternatively ligth two LEDs while using a toggle switch with
momentary contacts (normally off)? I would usually use change

over

relays but they are expensive and I know that transistors can be

used

to drive the DC current used for the LEDs.

Thank you very much,
Marco
PS Ok, I know a little, but just a little.

I don't completely understand what a 'change over relay' is.

can you make a little sketch and post it in the files section of

the

website ? please don't attach it as not all of us receive

attachments.

In very simple terms a transistor can be used like a switch. you

put a

signal onto it, and it passes a larger signal. remove the signal

and

the larger signal stops.

if you mean to have a switch to light an LED, why not just use the
switch itself ?

Do you want to push a button to momentarily send a signal and then

the

larger signal is sent until the button is pushed a second time...

As you can see, there is a little info lacking to be able to offer

advise.

Dave

What he needs is a T type flip flop. Or a D flop with the D input
connected to Q'. In either case, the clk input comes from the
momentary switch - debounced of course.

--- In Electronics_101@..., Marco Scuderi
<scudhome@y...> wrote:

A Double Pole Change Over relay is just a solenoid attached to two

poles. A momentary action of the solenoid moves the two poles and a
spring holds them in the new position even after the pulse to the
solenoid has ceased. A new pulse and the poles will move and stay in
the opposite position - so to speack.

I need to use the toggle switch to protect the rest of the

circuit. At the same time I'd like two LEDs to stay brigth - one at
a time - to tell me what the previous action of the toggle switch
was.

I used transistors but I cannot figure out how to organize them as

to have the base constantly on or off with just a toggle switch.

I think T type flip flop will do the job, if I can understand how

to use them.

See the bistable flip-flop here:


Any NPN transistor should work: try something like a 2N2222A or a
2N3904.

Thank you all, I apreciate your help.

rtstofer <rstofer@p...> wrote:
--- In Electronics_101@..., "Dave Mucha"
<dave_mucha@y...> wrote:

--- In Electronics_101@..., "scudhome"

<scudhome@y...>

wrote:

Hi there,
I know nothing about electronics other than it would be a

whole

lot

cheaper to by 100 transistors rather than 100 DPCO relays...

Could anyone please explain how I could use transistors to
alternatively ligth two LEDs while using a toggle switch with
momentary contacts (normally off)? I would usually use change

over

relays but they are expensive and I know that transistors can

be

used

to drive the DC current used for the LEDs.

Thank you very much,
Marco
PS Ok, I know a little, but just a little.

I don't completely understand what a 'change over relay' is.

can you make a little sketch and post it in the files section of

the

website ? please don't attach it as not all of us receive

attachments.

In very simple terms a transistor can be used like a switch. you

put a

signal onto it, and it passes a larger signal. remove the

signal

and

the larger signal stops.

if you mean to have a switch to light an LED, why not just use

the

switch itself ?

Do you want to push a button to momentarily send a signal and

then

the

larger signal is sent until the button is pushed a second

time...

As you can see, there is a little info lacking to be able to

offer

advise.

Dave

What he needs is a T type flip flop. Or a D flop with the D input
connected to Q'. In either case, the clk input comes from the
momentary switch - debounced of course.






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On Monday 25 July 2005 10:12 am, rtstofer wrote:

See the bistable flip-flop here:


Any NPN transistor should work: try something like a 2N2222A or a
2N3904.

Bunches of good stuff on those pages...

Chris, you might take a look at these, too. :-)

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In a message dated 7/25/2005 11:00:36 A.M. Central Daylight Time, julcat@... writes:

I put a little schematic here:

Giuliano!!? Ideal!? Correct!????????????Jan Rowland

On Monday 25 July 2005 11:59 am, Giuliani wrote:

Hi Marco,
I put a little schematic here:

May be it is what you are looking for.

Looking at that, I was thinking of some variations on the circuit...

Suppose instead of a bipolar transistor driving a relay, you used just a FET.
Maybe some kind of a power FET. The circuit could then be used for
controlling the power to a bunch of other stuff, toggling on and off states,
and "off" would only draw as much current as the 4093 needed while in a
static condition, or not very much at all.

What do you guys think of that idea?

On Thursday 31 May 2001 06:29 am, Giuliani wrote:

Yes, I have already tested it. Here the schematic.


The 4093 sinks only a few microamperes.

Bye.
Giuliano

Any thoughts on what would be a reasonable power drain with any given FET? I
have some small-signal ones, and some medium-power ones (TO220 pkg) that
I've salvaged...

----- Original Message -----
From: Roy J. Tellason
To: Electronics_101@...
Sent: Tuesday, July 26, 2005 9:13 PM
Subject: Re: [Electronics_101] Re: How to (replace DPCO relays with
simple transistros)

Looking at that, I was thinking of some variations on the circuit...

Suppose instead of a bipolar transistor driving a relay, you used just a
FET. Maybe some kind of a power FET. The circuit could then be used for
controlling the power to a bunch of other stuff, toggling on and off
states, and "off" would only draw as much current as the 4093 needed while
in a static condition, or not very much at all.

What do you guys think of that idea?









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