DIODE confusion

[avag...@gmail.com]

http://ecetutorials.com/wp-content/uploads/2013/10/diode-symbol.jpg

I'm reading isolating 12V fields with a diode places the band toward ground

but isolating ground leads past a power drop device from 12V isolates with band toward the device away from ground.

is this true or false ? exceptions ?

...........................

[Pat]

I have no idea what you are talking about. What is a 12V field? What
is a power drop device? Diodes pass current in one direction (toward
the band) but not the other. They can be used for all sorts of
purposes, but I really don't understand what you are trying to do.

[Phil Allison]

** All depends which end of the diode the band is on ...



... Phil

[avag...@gmail.com]

wiring relays in a vehicle alarm circuit, I was isolating flow with open diode end always facing the 12V supply wether diode was before a sensor or horn or after on the ground side.

then I read that ground side diodes are wired with the diode open side facing the ground with the band facing the sensor or horn ...

?

[amdx]

Still don't have enough info. There are two possible uses that I see
from the limited info.
The diode could be used to protect the relay driver from the voltage
spike generated when you remove current from the relay coil.
In that case the diode is across the relay, reverse biased when the
diode is energized.
I can't think why, but you could be using diodes to steer current, so
that, if this is on, that is not on, or some such thing. That you just
need to figure out.
A schematic of your circuit would provide you with an answer.
Mikek

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[avag...@gmail.com]

Right in both suggestions.

The overall problem is the siren in the engine area grounded to fender does not so far accept a relay connection for 12v from battery using 12v from alarm brain for switching batt power...

But to my delight and amazement, 2 rear roof mounted relays transfer 12v batt power with the brain's 12v signal.

The brain 12v all wire onto the same block terminal.

Lookin for an answer in text or image before trial n E, I ran into poor English probably from Korean..."when switched ground" then the rule for mounting diodes on power from batt with open end toward power
and on the ground side mounted opposite with open diode side toward the physical ground side.

If that is true then not only have I isolated field areas incorrectly but am missing basic theory on how ground functions

[amdx]

Can you make a drawing of the circuit.

Mikek

[avag...@gmail.com]

oh sure but the question was is the statement abt diode position visavee 12V and ground valid ? as a rule ?

I see the problem in my wiring that is all relay direct power switching is done on the ground side of the load. Optimism !



http://www.caraudiohelp.com/images/relay_for_remote.gif

big deal.

if I wanted to isolate this relays ground from the other grounds on the local ground bolt, I would wire in a diode with

the stripe facing the relay

or the stripe facing away from the relay ?

[M Philbrook]

In article <0cec50d3-7e01-42a4...@googlegroups.com>,
avag...@gmail.com says...

I am not exactly sure what you are doing but, It seems to
me you are trying to piggy back on a existing circuit via
a relay contact but you don't want the control signal to
get crossed over ?

For diodes. the line side of the DIODE (K) is the side that
will block (+) volts and the non-line(A) will block (-) volts, so
no current will flow.

This means if you were to place a diode (K) to the (+) side
and (A) to the (-) side of a battery, no current will flow through
the diode.

btw, the relay you pointed to uses automobile number codes, this
generally means there is a code number that specifies a function
of that wire.. Funciton, not an ID of the wire..norminal number
per function. Not to get confused with cardinal or ordinal number
types.

The numbers you see printed beside the stabs on the relay indicate
the use. This does not mean you have to follow that.

[avag...@gmail.com]

right...well written.

It seems to
me you are trying to piggy back on a existing circuit via
a relay contact but you don't want the control signal to
get crossed over ?

correct. My DIY alarm system is grafted onto a factory system, an Omega, with diodes. If it doesn't work throw diodes at it.

The de riguer roof mounted desert driving lights ground thru 5 relays into a dimmer switch on the way to the brake from throttle. Was interesting testing that seeing it gradually not work from relay to relay.

searching thru schematics in Google Images I found diodes for multiple triggers. Now how would I know what a trigger is ...?

EHHEEYAYYAY it works !.


Here, I wired into a morass then tried finding an explanation for the problem running into 'switch to ground', what seems a backwards English description of ? and other confusion.

English EEE is difficult and examples are herein.

The system is in a van. In the beginning wire 2 sizes larger than factory eg Hella wires seemed adequate then Liebermann suggested Powerstream for a kayak inverter. Once there I found the wire size calculator then Hella's point that a small voltage drop from 12V looses 30% of the light source.

The alarm sirens and horn are powered now.

Relays work with 8 and 10 Ga using the smaller wire for a signal.

[amdx]

If by signal you mean the wire that energizes the coil, it can be a
lot smaller than 10ga. The coil may draw something like 120ma, so the
wire diameter can be small.

There are two ways to power a relay.
1) You connect one side of the coil to ground and then switch +12V to
the other side.
2) You connect one side of the coil to +12V then switch the other side
to ground.
A diode will allow current to flow if the voltage is higher on the
anode than on the cathode. Current will not flow if the voltage is
higher on the cathode than on the anode.

Has your original question been answered?

If you want an answer you need to ask one question and give enough
details so we know what you are trying to do.