Mounting the LEDs
The choice of how you mount the LEDs is up to you. The suggested panel design uses the four
LEDs used in the signal meter going up at a forty five degree angle and has the power LED on the
central horizontal axis of the panel in line with the pot shafts. It does, however, make it easier if you
just fit all the LEDs in a straight line just above the board's top surface. Whichever way you chose
you must remember that LEDs are diodes and should be fitted the correct way around or they will
not light up. Check the data sheet for the devices you have bought to see which lead is the cathode.
The cathode should be soldered to the square pad on the PCB.
The key about mounting an LED to any front panel is to make sure it won't push into the unit when
force is applied to it from the front. There are several ways to do this, LED clips, glue (no don't do
this), or just relying on the stiffness of the leads. For the second SRE330 prototype I mounted the
LEDs onto a bit of stripboard. Stripboard, or Veroboard, is a laminated paper based printed circuit
board with copper strips on one side and perforated by a 0.1” grid of holes into which you put the
component leads through. You can cut it to size by using a knife to score along the holes on both
sides and then snapping the board along the score. The rough edges can be filed down to make a
nice tidy little board useful for prototyping. Or fitting LEDs.
The power on LED.
The power on LED is fitted to small piece of stripboard secured very firmly by a two way right
angled board to board connector. The right angled connector is soldered first to the stripboard and
then to the SRE330 main board. The LED is poked through, making sure the leads are correctly
polarised, and then soldered in place only when the front panel is fitted and the LED is at the correct
depth into the panel's hole. The photo shows how the right angle board to board connector fits into
the main board and the stripboard with the black plastic part up against the main board. The copper
strips are vertical to allow the LED to connect with the board to board connector.
The four LED signal meter was done similarly and, although fiddly to make, proves to be very
sturdy and effective. This time the right angled board to board connector was soldered up against