Regulating Voltage with LM78XX

[John Popelish]

Chris wrote:
(snip)

I'll bet you would have made a heck of a science teacher in another
life, Mr. Popelish.

I was laboring under the impression that I am a fair science
teacher in this life. Unpaid, however.

 

[jasen]

X-Face: ?)Aw4rXwN5u0~$nqKj`xPz>xHCwgi^q+^?Ri*+R(&uv2=E1Q0Zk(>h!~o2ID@6{uf8s;a+M[5[U[QT7xFN%^gR"=tuJw%TXXR'Fp~W;(T"1(739R%m0Yyyv*gkGoPA.$b,D.w:z+<'"=-lVT?6{T?=R^:W5g|E2#EhjKCa+nt":4b}dU7GYB*HBxn&Td$@f%.kl^:7X8rQWd[NTc"P"u6nkisze/Q;8"9Z{peQF,w)7UjV$c|RO/mQW/NMgWfr5*$-Z%u46"/00mx-,\R'fLPe.)^
User-Agent: slrn/0.9.8.1 (Debian)

idea how to determine them. The circuit just said 12V for the relay and
I have read the other posts and it seems as if relays are not all that
sensitive,

true, if you have a 12V relay, measure its resistance, halve that and put a
resistor approximately that size in series with the relay (+/-10% is close
enough). you can treat the combination as an 18V relay

as long as whatever that's going to be sqitching the relay on and off can
handle 18V instead of 12V you'll have no problems.

Bye.
Jasen

 

[Don]

Hi, Mr. Popelish. Your spell checker was happy because "minutia" is
singular, and "minutiae" is plural. Talk about minutiae! ;-)

Getting the relevant information from the OP seems to be like pulling
teeth. I'll bet that when he's done, his best solution would be a
simple Time Delay Relay (TDR). Power it up with DC or AC, and you get
a two hour timed relay contact closure. The OP might want to check out
SSAC for some good inexpensive ones that should do the job:

http://www.ssac.com/

But the education is in the journey, not just the destination. You
seem to enjoy this stuff more than just about anyone in the newsgroups.
I'll bet you would have made a heck of a science teacher in another
life, Mr. Popelish.

Cheers
Chris

I am the OP and the circuit is from:

http://www.zen22142.zen.co.uk/Circuits/Timing/24hour.htm

I wanted the circuit to shut off a 120V outlet after 2 hours.
(I'll google a time delay relay), sometimes you just don't know the key
word to query?

I do not know much but how to follow a simple schematic is sometimes
taxing to me, as are most things to do with math. I was assaulted three
years ago and suffered at least one concussion, and three skull
fractures which has left me with about 20% of what I had for brain power
and remembering shit. I'm not complaining, just living with it and doing
the best I can.

Thanks for all the responses. I had not seen many options for any timer
over 60 seconds much less the 2hrs that I need. Funny thing is that I
was a programmer for 36 years, and I can still do that, although it's
very slow. Analogy is I used to be a brick layer that could do 1000
bricks a day, now I can struggle and do 200. I can still do it but much
too slow to work it as a profession any longer.

Thanks again for all the help; Don

 

[Chris]

I am the OP and the circuit is from:

http://www.zen22142.zen.co.uk/Circuits/Timing/24hour.htm

I wanted the circuit to shut off a 120V outlet after 2 hours.
(I'll google a time delay relay), sometimes you just don't know the key
word to query?

I do not know much but how to follow a simple schematic is sometimes
taxing to me, as are most things to do with math. I was assaulted three
years ago and suffered at least one concussion, and three skull
fractures which has left me with about 20% of what I had for brain power
and remembering shit. I'm not complaining, just living with it and doing
the best I can.

Thanks for all the responses. I had not seen many options for any timer
over 60 seconds much less the 2hrs that I need. Funny thing is that I
was a programmer for 36 years, and I can still do that, although it's
very slow. Analogy is I used to be a brick layer that could do 1000
bricks a day, now I can struggle and do 200. I can still do it but much
too slow to work it as a profession any longer.

Thanks again for all the help; Don

Hi, Don. Your link to the 4060-based timer circuit explains a lot.
Yes, you do need a steady DC supply if you're going to use this circuit
(which is similar to the standard Time Delay Relay module of the 1970s
and early '80s). Your circuit will cost a lot less than a TDR,
especially if you've got the 12V coil relay in your junkbox, and it
should work well. You also need a voltage within +/-20% of the nominal
relay coil voltage when the relay is on. So it might be best to just
go with a regulated output +12V supply, like another post suggested.

Good luck with your project. I shouldn't have cast aspersions -- how
should a newbie be expected to know the right way to phrase a question
unless he already pretty much knows the answer? This ain't Plato's
Cave, it's just a newsgroup.

http://en.wikipedia.org/wiki/Plato's_cave

Cheers
Chris

 

[John Popelish]

I am the OP and the circuit is from:

http://www.zen22142.zen.co.uk/Circuits/Timing/24hour.htm

I wanted the circuit to shut off a 120V outlet after 2 hours.

(snip)

Thanks for the link. Now we know what you are talking about.

The cmos counter chip (CD4060, with 16 pins)
http://www.intersil.com/data/fn/fn3317.pdf
can operate over a wide range of about 3 to 18 volts.
However, the timing stability of the oscillator section made
up of two inverters and an RC feedback network) will be
better above about 5 volts.

What DC voltage source do you have available to drive this
circuit (between the +VE and -VE terminals on the schematic)?

Ideally, you should pick a small relay that matches that
supply voltage.

Here is an example of a digital time delay relay that has
something like this circuit inside it:
http://web6.automationdirect.com/ad...er_Relays_1-z-16_DIN_(MS_Series)/MS4SM-AP-ADC

 

[Don]

Hi, Don. Your link to the 4060-based timer circuit explains a lot.
Yes, you do need a steady DC supply if you're going to use this circuit
(which is similar to the standard Time Delay Relay module of the 1970s
and early '80s). Your circuit will cost a lot less than a TDR,
especially if you've got the 12V coil relay in your junkbox, and it
should work well. You also need a voltage within +/-20% of the nominal
relay coil voltage when the relay is on. So it might be best to just
go with a regulated output +12V supply, like another post suggested.

Good luck with your project. I shouldn't have cast aspersions -- how
should a newbie be expected to know the right way to phrase a question
unless he already pretty much knows the answer? This ain't Plato's
Cave, it's just a newsgroup.

http://en.wikipedia.org/wiki/Plato's_cave

Cheers
Chris

Chris;
(I looked at the link for the time delay relays, they did look a bit out
of my budget).
No aspersions were ever taken or considered, but I did fail to mention
the circuit, (not intended but, pretty vague on my part). I usually over
do it on information since in my old job (as here) it was so very
important to be precise and not be led down the river of no return, "He
who fails to plan, plans to fail". I dug up my last 7812 and I have a
full wave bridge, now its up to me to get everything in the right
direction and place. You all have been very helpful, and I appreciate
all the time and effort/knowledge that is required to respond to my
posts. Too often, someone gets help and does not even have the decency
to say a simple thank you, I hope I said it well enough!
Thanks to all and I certainly appreciate all the help;
Don

 

[Don]

(snip)

Thanks for the link. Now we know what you are talking about.

The cmos counter chip (CD4060, with 16 pins)
http://www.intersil.com/data/fn/fn3317.pdf
can operate over a wide range of about 3 to 18 volts. However, the
timing stability of the oscillator section made up of two inverters and
an RC feedback network) will be better above about 5 volts.

What DC voltage source do you have available to drive this circuit
(between the +VE and -VE terminals on the schematic)?

Ideally, you should pick a small relay that matches that supply voltage.

Here is an example of a digital time delay relay that has something like
this circuit inside it:
http://web6.automationdirect.com/ad...er_Relays_1-z-16_DIN_(MS_Series)/MS4SM-AP-ADC

Thanks for the link, I was going to get a 12-18V transformer and the
relay is 12v and I have my last 7812 available and all the other parts.

 

[Don]

John;
Thanks for the insight and link! (hindsight foresight comes into play
here since I can get the whole package for under $50).
Thanks again, I have bookmarked the page for my next easier project, all
in one!
Thanks again; Don

 

[jasen]

idea how to determine them. The circuit just said 12V for the relay and
I have read the other posts and it seems as if relays are not all that
sensitive,

true, if you have a 12V relay, measure its resistance, halve that and put a
resistor approximately that size in series with the relay (+/-10% is close
enough). you can treat the combination as an 18V relay

as long as whatever that's going to be sqitching the relay on and off can
handle 18V instead of 12V you'll have no problems.

Bye.
Jasen