PhotoFet True Bypass Relay v1.0.1
6
Now, start by soldering the resistors and
D1
and
D2
on the
top-side
. You can experiment with the
value of
R1
. If the LED is to dim, lower the value up to 1k5 to make it brighter, but do remember that
the brighter you set the LED, the shorter it’s
lifespan and the more power it consumes.
Next, solder
IC1
(pin 1 is marked by the square pad),
OC1
(pin 1 is marked by a dot) and
VR1
, all on
the top-side. Make sure you cut the leads as short as possible on the bottom side without breaking
any solder points. This is important as we will be sticking the switch to the bottom of the PCB later
and we want to save as much space as possible. Solder
C1
and
C2
and
REL1
to the
bottom side
.
Now, something about the photocoupler.
R2
determines the reaction time in relation to the
brightness of the LED inside the photocoupler. I tested a lot of batches of TLP222A and they all seem
to work fine with a 1k5 resistor at
R2
. However, if you are using a different photocoupler for example
a TLP222G, the value can be different. If the photocoupler is configured incorrect, you will hear the
loud
“pop” again when switching the effect on and off.
Having experimented with several different types and batches, you could try a value for
R2
between
1k5 and 2k2. When it does not pop anymore, you got the that value!
On a side note. The capacitance of a TLP222A (C
off
) is about 130pF where as a TLP222G is only 30pF.
This capacitance is in the off position of the photocoupler
OC1
. I could not really hear a difference,
but if you do, I would advise to use a TLP222G.
PS. I would stick to a TLP222A as it is cheap and works great!
