As link shows below does anyone know what the reason is for the relays with diodes on them.. i know if the diode is across the relay coil its a flyback diode but why the diode on one side of the contacts, i did see a post about the diode being used to latch the relay anyone know why theres a diode...?
https://www.google.co.uk/search?q=c..._AUIDigB&biw=960&bih=474#imgrc=0ErWLByLwxTY-M:
Al.
that link you have posted shows the terminals in a different layout (Type A),
the diode is still on the coil.
There are two types of relay pin layout Type A as above, and the 'normal" Type B where the 30 terminal is in line with the output terminals, and the coil connections are on opposite sides
Don't forget that 85 and 86 are always the relay coil terminals. if there is a diode across the coil it can also be designated 86b
According to DIN 72552 the coil should be fed with +12V to terminal 86 and grounded via terminal 85.
In practice it makes no difference which way around they are wired, unless you are using a relay with an integrated diode, because the relay will still switch, but the diode will have no effect
30 is the source that you want to either switch
on, through the normally open contact 87,
or switch
off, through a normally closed contact 87a (sometimes 87b)
The diode is to stop back feed of voltage from the coil itself as it de-energises, which can be classed as a 'spike'
You can still make a relay latch in various ways without a diode, for example by connecting the coil positive 86 to a switched positive on 87.
