On Thu, 14 Dec 2006 22:45:44 GMT, "SBFan2000"
wrote:
"Ross Herbert" wrote in message
.. .
On Thu, 14 Dec 2006 02:02:22 GMT, "SBFan2000"
wrote:
I did pick out final components except for the relays. I'm not entirely
understanding how they are rated. I left room on the PCBs to accomidate
most relays pins. I had a good idea of the voltage I wanted to use. I
had
selected 24vdc but was wondering if 12 or 18vdc would be enough.
Basically I want a button that I push on a "control panel" to travel the
100ft to a relay which then turns on a 115vac supply. Like I said I'm
having issues understanding the way relays are rated. Assuming I go with
24vdc I would need a relay with a coil rated at 24vdc and a N.O. switch
that
can handle 115vac at 10-20A, correct?
On reading the explanation of the type of load you wish to drive (last
paragraph below) it seems I may have interpreted that you wanted the
relay contact to control the 115Vac output.
When you said "I would need a relay with a coil rated at 24vdc and a
N.O. switch that can handle 115vac at 10-20A, correct?" I thought you
were referring to the N.O. contact on the relay as the "N.O. switch"
which needed to be rated for 115Vac at 10 - 20A, but it appears that
the N.O. switch you were referring to may be the switch used to cause
the operation of the 24V relay at the remote end of the 100 ft cable.
Is this correct?
The switch used to control the relay coil only needs to be capable of
handling a maximum of 1 - 2A at the operating voltage of 24Vdc. It
won't matter if you do use a higher rated switch for this function.
A sketch of what you are trying to achieve would be helpful.
You could use any voltage you like depending upon what guage wire you
use for the 100ft link. Generally any voltage from 12V - 24V would be
quite suitable if you use twin conductor cable with conductors of
0.4mm (26AWG) diameter (or better) copper.
Understood
All leds are either red or green and based on what I read are 2vdc at
.020mA. I do have 3-4 blue leds which I read at 4vdc and .040mA (if
memory
serves) Could you explain "in series" and "in Parallel." The way I
understand it (and I could be wrong) Parallel would be having power go
from
one led to the other in a chain? Serial would be a home run track, back
to
power, for each led. In this case parallel is the way I did it. (with a
resistor for each led)
Oh dear me.... are you sure you should be getting into a project
involving 115Vac? If you don't understand what series and parallel
connections for low voltage components such as leds then you could get
yourself killed when playing around with lethal voltages and currents.
Have you tried doing some basic research into the meaning of these
terms? - Google is your friend...
Could you please explain series and parallel so I can verify what I have
already researched and read on the subject instead of just saying that if I
don't understand it I'm to stupid to deal with it?
Basic explanation of series and parallel circuits
http://www.allaboutcircuits.com/vol_1/chpt_5/1.html
Connecting LED's in series (20mA types)
http://unclean.org/howto/led_circuit.html
If you haven't been here then it is a good place to start
http://led.linear1.org/
They have a LED series parallel calculator wizard
http://led.linear1.org/led.wiz
I would never connect leds of different colours in a series string
because they all have different voltage requirements. I would only
connect leds of the same colour in any individual series string.
I didn't. I have three different colors but no colors are mixed with other
colors. Both my red and green leds are all 2VDC and the 3 Blues are 4VDC.
Technically I could connect the red and greens but I didn't. Every single
LED in the system also has its own dedicated resistor. I'm not using one
resistor for the entire string because (from what I researched) a led with
slightly different requirements could burnout. This thing already has
almost 100 resistors if that give you an idea of the LEDs required.
Try using the LED calculator wizard in the link above to check out the
circuit arrangement for each of the LED colour arrays you are
building.
I didn't mean to imply that the PCBs are totally done. They are merely
to
the point where I can no longer put off relay selection. That all said,
I
don't doubt I'm doing things wrong and backwards, it is my first PCB from
scratch. (I've repaired them at work)
How about these:
http://cgi.ebay.com/Tyco-Relays-SPST...PCB_W0QQitemZ1
20060224418QQihZ002QQcategoryZ42897QQrdZ1QQssPage NameZWD1VQQcmdZViewItem
It depends on what type of load you are planning to control with the
relay output. That particular relay is only rated to switch 10A @
250Vac into a resistive load. Also, it can only switch a maximum load
of 280W. You would not use it to control an inductive load such as a
115Vac electric motor or pump.
10A should be fine. Just using standard home outlet to supply this thing.
I can make sure I use a 10 breaker or I can build a 10A (or slightly less)
fuse into the system.
See full data sheet here
http://relays.tycoelectronics.com/datasheets/OJ-OJE.pdf
What type of load are you intending to drive?
Boy you'll love this, A short circuit! Basically a low gauge wire
connected to positive and negative that will burn up when the relay is
tripped. A light bulb with out the glass, basically. I should say that I
have already built this and used it twice it works quite well. The current
system uses 115Vac at 15A for the entire system. I'm just redesigning to
get the controls and the majority of the rest of the system at lower
voltage. I thought of using 24VDC for the whole thing but a trace on one of
the boards could burn up instead of the filament. Thats the reason for the
relays to isolate the short from the rest of the system. I suppose I could
have one PSU (24VDC) for the system side and another for the "short" side.
it would be slightly safer. :-)
You will needa separate low power 24V dc supply to drive the relay
coil - 100mA output capability would be suitable for the relay you
have nominated.
Use a separate high power 24V dc supply for the output (load side).
This will need to be a fairly robust supply and may not need to be a
regulated supply - a simple brute force mains transformer, bridge
rectifier and filter capacitor arrangement with a hefty output circuit
breaker or fuse (say 50A).
The problem I see for the relay you have nominated is that the relay
contacts will either be welded together or simply blasted away as soon
as they make to supply 24V to the short circuit load. It is not going
to be suitable for what you want to do. A pcb mounted relay will not
be the way to go.
For the function you require to perform you need a heavy duty
contactor or mercury relay to handle the fast high current surge you
will produce.
Something like these would be suitable
http://www.tempco.com/Accessories/Me...ent_Relays.htm
Note: to drive the 24V dc coil of a RLY01355 (35A rating) you would
need a 24Vdc coil supply capable of around 250mA.