On Fri, 6 Sep 2013 13:37:42 -0700, "Guv Bob"
wrote:
"Jim Thompson" wrote in message ...
On Fri, 6 Sep 2013 09:57:57 -0700, "Guv Bob"
wrote:
"Jim Mueller" wrote in message eb.com...
On Thu, 05 Sep 2013 13:47:53 -0700, Guv Bob wrote:
"Guv Bob" wrote in message
news
"RosemontCrest" wrote in message
...
On 9/4/2013 3:40 PM, Guv Bob wrote:
My component level electronics is rusty, including RC circuit
calculations, having been doing module swapping for years. This is
probably a very simple question for the folks here....
Is this a reasonable circuit for a delay timer?
If so, how would I calculate the values of R &C for this...
1. Switch closes 2. After 5 seconds, the relay energizes and
remains energized until switch is opened.
Sketch...
http://img839.imageshack.us/img839/4650/uh3.gif
Thanks in advance!
Bob
What is the minimum activation voltage of the relay coil? What is the
maximum coil voltage of the relay? What is the typical resistance of
the relay coil?
I'm using the relay shown in this MK111 circuit...
http://www.vellemanusa.com/downloads...nual_mk111.pdf
PS -- Photo of relay and data sheet attached.
Relay characteristics aren't controlled closely. As long as they meet
the guaranteed specs, that's all that counts. Anything better than that
is OK. This means that the circuit you propose can have a different
delay if you substitute another relay, even if it is the same type.
Therefore, you really can't calculate the values unless you measure the
characteristics of the particular relay you are going to use. It would
be easier to just try different values of the parts until you get the
result you want. As someones else pointed out, even then the results are
likely to be inconsistent.
This is the problem that 555 timer ICs solve. Consider using one.
--
Jim Mueller
To get my real email address, replace wrongname with dadoheadman.
Then replace nospam with fastmail. Lastly, replace com with us.
Thanks Jim. I have no experience with 555 timers. Where would I find a basic circuit for this application using a 555?
We know the coil of your relay of choice is 12VDC, but not how much
current is required (resistance of coil, or spec current).
It could be as simple as an R/C plus a 555, plus a diode, or it might
need a transistor as well.
That would be great! The 12VDC relay coil requires 38ma to actuate.
Are you actually using a relay to power an LED, or is that just a
representative load?
For an LED only, you don't even need the relay. How much current in
the LED?
...Jim Thompson
--
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