Footswitch-able FET Boost

[Matt J]

Sorry for posting the files, Martin! I have removed them!

Thanks for your answer! That makes things a little clearer and I'm going to try to draw out a diagram of it. Should the fact that I'm using 5v relay instead of 12v impact the value of the 1k dropping resistors?

- Matt J.

[martin manning]

Should the fact that I'm using 5v relay instead of 12v impact the value of the 1k dropping resistors?

Yes, of course. Easy to calculate: Rl = (Vs - Vf)/If , where Vs is supply voltage (5V), Vf is LED forward voltage (depends on color), and If is forward current. For example, a red LED's Vf is about 2V. For If, most small (3-5mm) LED's are limited to 30 mA, and you might want to reduce the brightness, so let's say 20mA. Rl is then 150Ω.

[Matt J]

Yes, of course. Easy to calculate: Rl = (Vs - Vf)/If , where Vs is supply voltage (5V), Vf is LED forward voltage (depends on color), and If is forward current. For example, a red LED's Vf is about 2V. For If, most small (3-5mm) LED's are limited to 30 mA, and you might want to reduce the brightness, so let's say 20mA. Rl is then 150Ω.

Thanks for the formula, Martin! Applying that, I'm getting about 230Ω for the LEDs I have to use. They're 3mm sized, red, green, and yellow from Amplified Parts, but their data sheet does not show separate Vf or If by color variation.
https://www.amplifiedparts.com/products/led-3mm

- Matt J.

[norburybrook]

Thanks for posting this diagram up!

I've started work on my #183 build and plan on having a three-button pedal with FET being footswitchable, so this certainly helps! I'm using one of Taylor's boards from Amplified Nation which correspond to these layouts seen at multiple places here on the Amp Garage.

Has anyone drawn up the proper way to wire the DIN plug and footswitch internals with this type of design? I'm a little unclear on what needs to go from there and wanted to research it and ask around before I did anymore soldering!

- Matt J.

Matt,

I'm doing the same thing at the moment with my build. I'm having some relay issues but here's the footswitch wiring

3 switch footswitch wiring.bmp

the purple wire is the power , the black is ground the rest are each individual relay.


M

[Matt J]

Matt,

I'm doing the same thing at the moment with my build. I'm having some relay issues but here's the footswitch wiring

3 switch footswitch wiring.bmp

the purple wire is the power , the black is ground the rest are each individual relay.


M

Thanks for the diagram, M!

Exactly what type of relay issues are you having and did you end up using 1K resistors for each LED, or separate values based on their color?

- Matt J.

[norburybrook]

Matt,

I'm doing the same thing at the moment with my build. I'm having some relay issues but here's the footswitch wiring

3 switch footswitch wiring.bmp

the purple wire is the power , the black is ground the rest are each individual relay.


M

Thanks for the diagram, M!

Exactly what type of relay issues are you having and did you end up using 1K resistors for each LED, or separate values based on their color?

- Matt J.

Matt,

basically I had polarized relays and that meant the board markings and the layout were the wrong way round...who knew? I didn't realise the same Omron relays came polarised and non-polarised. For future reference always get non polarised.

I've just wired up my switch and I'm going to have to do some tweaking the first LED is really bright and the last is dim.

I have 1k on all of them.


M

[Matt J]

Matt,

basically I had polarized relays and that meant the board markings and the layout were the wrong way round...who knew? I didn't realise the same Omron relays came polarised and non-polarised. For future reference always get non polarised.

I've just wired up my switch and I'm going to have to do some tweaking the first LED is really bright and the last is dim.

I have 1k on all of them.


M

Hmm... I never realized that about some Omron relays. I'm using them in my build as well. Are these the same type you are using? I plan on testing the switching system later today and I don't want them to be backwards when I start testing things!

- Matt J.

[norburybrook]

Matt,

basically I had polarized relays and that meant the board markings and the layout were the wrong way round...who knew? I didn't realise the same Omron relays came polarised and non-polarised. For future reference always get non polarised.

I've just wired up my switch and I'm going to have to do some tweaking the first LED is really bright and the last is dim.

I have 1k on all of them.


M

Hmm... I never realized that about some Omron relays. I'm using them in my build as well. Are these the same type you are using? I plan on testing the switching system later today and I don't want them to be backwards when I start testing things!

- Matt J.

this is what martin said in reply to my issue.


There are several Omron relays of this basic type. In the ones you have there G6A-234P-ST15-US, the coil terminals are polarized, where the part number in my drawing G5V-2-H1-DC12, is non-polarized


I have no idea without going to Omron web site what it is that tells you if it's polarised or not from the serial numbers.


M

[pompeiisneaks]

That one you just showed is polarized. Look at the diagram for the leftmost pins, it shows a + at the top and a - at the bottom.

This means they're polarized and you need to connect the input to the + side (top in your pic) and ground to the - side.

norburybrook, sorry I was trying to explain that earlier as a possibility but may have done it poorly. Mine was polarized too and inverse of the common setup for the dumble ones. So I had to swap power and ground connections and I was set.

~Phil

[Matt J]

That one you just showed is polarized. Look at the diagram for the leftmost pins, it shows a + at the top and a - at the bottom.

This means they're polarized and you need to connect the input to the + side (top in your pic) and ground to the - side.

norburybrook, sorry I was trying to explain that earlier as a possibility but may have done it poorly. Mine was polarized too and inverse of the common setup for the dumble ones. So I had to swap power and ground connections and I was set.

~Phil

Thanks for the clarification, Phil!!

Looks like I've got some resoldering to do!

- Matt J.

[norburybrook]

That one you just showed is polarized. Look at the diagram for the leftmost pins, it shows a + at the top and a - at the bottom.

This means they're polarized and you need to connect the input to the + side (top in your pic) and ground to the - side.

norburybrook, sorry I was trying to explain that earlier as a possibility but may have done it poorly. Mine was polarized too and inverse of the common setup for the dumble ones. So I had to swap power and ground connections and I was set.

~Phil

Thanks for the clarification, Phil!!

Looks like I've got some resoldering to do!

- Matt J.

better now than when everything is crammed into a small space....nightmare...


thanks Phil for the explanation that makes sense.


You learn something every build you do,

[Matt J]

I've decided to pick up some NTE 5v non-polarized relays and use those. I've been needing to order some stuff from NTE so I lumped them in with my order. I don't want to dig into anything just yet because I'm out of desoldering braid and want to be careful with heating up parts on those PCB relay boards. I accidentally cooked one and ruined one of the traces on it a few years ago, so I'm a lot more cautious now.

While I'm waiting on my NTE shipment to arrive, I've been looking more at Martin's file that diagrams a footswitchable FET. I've tried drawing it out as a layout in Microsoft Paint to make things a little clearer, or to point out any errors or caution points I haven't spotted yet. All credit to Martin for creating the original layout! I used the FET board image from a #102 with a precision power supply file I've had for a while.

This is by no means an official document! Just let me know what you think. I've got a few days before I'll be doing any more soldering to ponder this over.

- Matt J.

[dorrisant]

I wonder if the polarized relays contain the diode you normally place across the coil terminals...

[martin manning]

The data sheet for the G6A relay doesn't mention a diode, so I wouldn't omit it. However, it does say "Unique moving loop (permanent magnet) armature reduces relay size, magnetic interference, and contact bounce time." Reverse polarity would repel rather than attract the armature, so it probably just doesn't work that way.

[dorrisant]

Should the jack in the OP be 11A(?), or 11, or more likely 12A?