Advice on Telephone Circuit

[Diefenbaker]

Im looking at building the Smart Phone Light.
http://www.electronic-circuits-diagrams.com//telephonesimages/12.gif

If anyone could answer a couple of questions.

I have tried to buy (C1) 1.u 400v Capacitor. But my local guys dont have
anything like this. Could I use something else. I did see 1u 250v but 400v
seems a little excessive, acept for spikes I suppose but I think everything
would go if it got that high.

Secondly I'm asuming that the (C3) +1000 could be a 16v cap.

Third the Relay I guess needs to be 5v relay. The diagram smudges the
number. But asuming that the trigering voltage there is 5v DC.

Finally, the circuit calls for
"A light dependent resistance (LDR), with about 5 kilo-ohms resistance in
the ambient light and greather than 100 kilo-ohms in darkness"

I have never bought LDR's it looks like you buy them based on ohms eg 100
ohms, since they are a resister. But I dont know what size to buy. Should I
get a 5k ohm or 100k ohm. Im not sure I know what to ask for?

One or any of the questions answered would be helpfull.

Thanks.

 

[Andrew Holme]

Diefenbaker wrote:

Im looking at building the Smart Phone Light.
http://www.electronic-circuits-diagrams.com//telephonesimages/12.gif

If anyone could answer a couple of questions.

I have tried to buy (C1) 1.u 400v Capacitor. But my local guys dont
have anything like this. Could I use something else. I did see 1u
250v but 400v seems a little excessive, acept for spikes I suppose
but I think everything would go if it got that high.

Yes, 250V would be fine.

Secondly I'm asuming that the (C3) +1000 could be a 16v cap.

Yes, 1000uF 16V is fine.

Third the Relay I guess needs to be 5v relay. The diagram smudges the
number. But asuming that the trigering voltage there is 5v DC.

Right again.

Finally, the circuit calls for
"A light dependent resistance (LDR), with about 5 kilo-ohms
resistance in the ambient light and greather than 100 kilo-ohms in
darkness"

I have never bought LDR's it looks like you buy them based on ohms eg
100 ohms, since they are a resister. But I dont know what size to
buy. Should I get a 5k ohm or 100k ohm. Im not sure I know what to
ask for?

The resistance of the LDR is not fixed! It varies with the incident light
level. It is quoted at one or more specific light levels (measured in lux).
As a guide, bright lighting for a workshop is about 2000 LUX. You want one
that is around 5k in ambient light and more than 100k in darkness. They
generally have very high dark resistance so you shouldn't have any problem
at that end of the scale.

 

[Andrew Holme]

Diefenbaker wrote:

"Andrew Holme" <andrew@nospam.com> wrote in message
news:cpq69k$9lm$1$8300dec7@news.demon.co.uk...
Diefenbaker wrote:
Im looking at building the Smart Phone Light.
http://www.electronic-circuits-diagrams.com//telephonesimages/12.gif

If anyone could answer a couple of questions.

I have tried to buy (C1) 1.u 400v Capacitor. But my local guys dont
have anything like this. Could I use something else. I did see 1u
250v but 400v seems a little excessive, acept for spikes I suppose
but I think everything would go if it got that high.

Yes, 250V would be fine.

Secondly I'm asuming that the (C3) +1000 could be a 16v cap.

Yes, 1000uF 16V is fine.

Third the Relay I guess needs to be 5v relay. The diagram smudges
the number. But asuming that the trigering voltage there is 5v DC.

Right again.

Finally, the circuit calls for
"A light dependent resistance (LDR), with about 5 kilo-ohms
resistance in the ambient light and greather than 100 kilo-ohms in
darkness"

I have never bought LDR's it looks like you buy them based on ohms
eg 100 ohms, since they are a resister. But I dont know what size to
buy. Should I get a 5k ohm or 100k ohm. Im not sure I know what to
ask for?

The resistance of the LDR is not fixed! It varies with the incident
light level. It is quoted at one or more specific light levels
(measured in lux). As a guide, bright lighting for a workshop is
about 2000 LUX. You want one that is around 5k in ambient light and
more than 100k in darkness. They generally have very high dark
resistance so you shouldn't have any problem at that end of the
scale.



Wow Thanks Andrew. Great info.

A clarification on the LDR. I see a ORP12 Part Number seems to be
common. Do you know whether that would be an apropriate part for this
project.

One place I saw, the following comments on the Orp12
a.. Darkness: maximum resistance, about 1M.
b.. Very bright light: minimum resistance, about 100.
As you said the dark side is less of an issue. I note that it says
very bright light so this may be ok in dusk to dawn times or if the
circuit more likely is in a house where the light will not be bright
but indirect.

Regards

I found the following data on the ORP12:

@ 10,000 lux 80Ohms.
@ 50 lux 6kOhms.
Dark resistance (min.): 1MOhms.

That sounds about right for your application.