Long time lurker drops in to ask a few Q’s regarding the footswitch or “remote” option.
I’m trying to build a footswitch for a #124-style amp that has a 5-Pin DIN connection on the back for remote switching.
My goal is to have two DPDTs alternate between PAB and OD selections (with LED indicators). The enclosure for the FTSW is a simple Hammond 1590B that has a built-in DIN jack (Mouser part# 502-61GB5FX) so that a MIDI cable can attach/detach itself from the unit.
Here’s my query:
Looking at the attached layout, would this effectively do what I want it to do?
The output of the 7812 on #124 shows two 1K resistors running to pins 1 & 5 on the DIN. Seems to me like those resistors limits currents to each Anode of the LEDs, preventing them from becoming DEDs (darkness emitting diodes ).
If I’m completely bonkers, would someone please point me in the right direction.
Happy Holi…err..building!!!
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Last edited by UltraHookedOnPhonix on Wed Feb 27, 2008 7:06 pm, edited 1 time in total.
I think the way to go if you are using SPDT switches is to wire the ground to the middle lug of the switch with the LED and relay wired to opposite ends. This works well and is easy on the power supply but the LEDs will be ON when the relays are OFF.
If you are using DPDT switches use one pole for the LED and the other for the relay. I'm working out a footswitch myself and so far I think this is the way I'm going to do it. You could also run a single wire from the regulator to the footswitch and split it inside the FS box for the LEDs. This would free up a wire in case you ever want to toy with a 3rd footswitch.
edit: After thinking about it for a few minutes, using SPDT switches you could wire both the LED and relay to the middle lug and ground to one end. That will turn them both on together.
Jonas wrote:My goal is to have two DPDTs alternate between PAB and OD selections (with LED indicators).
I haven't studied your drawing yet but I have a question about your comment. By "alternate" do you mean you intend to switch between PAB on OD off AND PAB off OD on, with one of the switches??
Jonas wrote: . . . so that a MIDI cable can attach/detach itself from the unit.
Just a side note: If you are actually planning to use a MIDI cable, it will likely not work. Most MIDI cables are only 3 conductor even though the plug is 5 pin.
The authentic footswitch configuration uses SPST and 5 wires.
I was shying away from MIDI cables because of this but after testing several cheapos (which are more readily available than "nice" ones) I've been reconsidering. I was worried that "in a pinch" I may end up having a hard time finding a 5 wire one. That doesn't seem to be an issue as I found no 3 wire ones at all. FWIW these were all sold as standard MIDI cables - not a special 2-way cable.
I've been looking at Neutrik Ether-Con as an alternative. The cables are kind of pricey but built very well and in a pinch you can use any standard RJ-45 cable.
OK, this is just my take, but it happens to also be the way Dumble does this. All you need are two SPST switches... If you get SPDT switches, you can use dual color LEDs, and if you have DPDR switches you can double them up for more reliability.
Anyway, here is the description:
1. Pins 1 and 5 of the DIN switch come from the 1K dropping resistors on the board. Via the DIN switch, connect those to the "+" end each LED in the footswitch.
2. Pin 3 carries the ground voltage. Wire that to the poles of the channel switching switch and to the PAB switch.
3. Pin 2 connects to the PAB relay and Pin 4 to the channel switching relay.
3a. Connect the wire from Pin 1 to the "+" side of the PAB LED. Run wire from the "-" end of the LED to the switch "ON throw" lug, and also connect the wire from Pin 2 there. When you ground that node, the PAB relay will energize and the PAB LED will light up.
3b. Connect the wire from PIN 5 to the "+" side of the channel switch LED. Run a wire from the "-" end of that LED to the "ON throw" lug, and also connect the wire from Pin 4 there. When you ground that node, the channel switch relay will energize and the channel switch LED will light up.
Below are two pictures, numbering system on the DIN jack at the amp, as shown, would be Pin 1 starting at 2 o'clock, etc., PIN 3 at 6 o 'clock, etc. The footswitch shown happened to have 2P2T switches, so I've doubled everything up so that if one side breaks, the other one (in parallel with it) hopefully will still work. Note that on each switch, one throw is left unused, highlighting the fact that all you need is a single throw (a simple ON-OFF system) to light up the LED and energize the relay at the same time.
Gil
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Jonas wrote:
The .01uF caps on the DPDTs in the picture, what are those for? Anti-pop?
I suppose, although I never had a popping issue with the relays without the caps. The caps will actually shunt any voltage transients to ground, so they prevent the relays from ringing (off and on) in case some weird stuff happens.
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