Footswitch/led/Weber low power relay qu &n

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bluesbear
I only work on Fender's
Posts: 516
(5/23/05 10:26 am)
Reply  Footswitch/led/Weber low power relay question.
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 Hi. I'm running a Weber low power relay with a footswitch in an amp I'm working on. For those who don't know, these are powered by the 6.3v filament circuit. The footswitch makes or breaks the voltage within the circuit to operate the relay. Since this is the filament circuit, it must be isolated from the chassis by using a stereo plug and jack. I'm adding an LED to the footswitch and I have a couple of questions.

First, can I use a DPDT switch with one leg of the 6.3v to both center terminals, one outer terminal to the other leg of the 6.3v (going to the other side of the stereo jack), and the other outer terminal going to one side of an LED, the other side of the LED through a third wire to ground? Would the voltage going to (or through) the LED cause the 6.3v winding in the PT to fry?

My other thought would be to use a 9v battery in the footpedal. I know that would work but, if possible, I'd sure rather run the LED off the power going through the pedal already.

Does anyone know if my plan would work safely, or have another idea how to accomplish this?
Thanks!
Dave
 
TryingToDo613
Junior tube assistant
Posts: 69
(5/24/05 8:37 pm)
Reply  (bump)
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 Hi everyone. I found this with the search and it was never answered. I've been looking at electromechanical relays to run pedals that I want to build into my amp. I guess from this post that Gerald is powering the switch with the filiment current, but this post brings up an interesting idea with running the LED through the pedal. I was planning to try a three pole switch and running a separate line from the power bar or even right off the in from the wall. There must be regulars here who put footswitches in amps and don't run the signal all the way to the pedal and back, yet Doug doesn't sell any relays that I can see. How do y'all do it? -613
 
gehicks
Senior tube assistant
Posts: 139
(5/24/05 8:46 pm)
Reply  Re: (bump)
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 I use two amps  
 
Lucid Alice
I will work on all amps
Posts: 329
(5/24/05 10:29 pm)
Reply  Re: (bump)
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 An LED only uses 20 to 30 ma. You need a resistor, around 470 ohms?, in series with the LED to limit the current. It would take a short on the hot side of the 6.3 volt coming in to fry the PT.

 
OldHouseScott
Hey get your own solder
Posts: 220
(5/24/05 10:34 pm)
Reply  Re: (bump)
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 If your heater winding is center-tap grounded, or if you have two 100 ohm balance resistors to ground, you should be able to do as you described with a DPDT switch, but you will need to add a resistor in series with the LED. Something between 220 and 470 ohms should give you enough program current through the LED. You might also want to put a regular 1N4001 in series with the LED, or reverse-biased in parallel, to prevent exceeding the PIV for the LED.

Note that if you have the two balancing resistors setup, when you activate the switch to turn on the LED, your balance will be skewed slightly because of the extra path to ground presented by the LED/diode/resistor circuit. This might cause the hum to increase due to the imbalance. If you have a grounded heater CT, this should not be an issue.

OldHouseScott
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TryingToDo613
Junior tube assistant
Posts: 70
(5/25/05 11:25 am)
Reply  the light bulb trick
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 I was thinking of making the whole gadget up on a radio shack PC board. Then I'd use clip leads with a light bulb in series to clip it to the last two filiments in the chain. If that's bad please tell me. In fact if you could tell me a "first go to here, then to there, then to there" kind of thing I would be eternally indebted to you. In fact I'd even send you a bunch of the 50 relays I just won on ebay if you like. The guys says he has tripped them with 6v. This would be a really cool thing for Doug to put on the Library page, how to use a relay to route signal two ways and light up an LED when you do it. -613
 
boogielicious
Senior tube assistant
Posts: 159
(5/25/05 11:38 am)
Reply  Re: the light bulb trick
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 Check out the Millenium Bypass on this site.

www.geofex.com/

Look under FX projects. He describes using a DPDT switch and and LED. He has the parts and layout already.

Scott
 
zachsdad
Senior tube assistant
Posts: 180
(5/25/05 2:33 pm)
Reply  Re: the light bulb trick
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 I think this will do what you want. All the signal is kept in the chassis. You can put more that one switch in each pedal if there is room. Just need one more wire per switch since ground and "hot (about 4.5VDC)" are already there. Use a relay with a 5 VDC coil and choose the resistor value for the brightness of the LED.

Good luck




img.photobucket.com/album...switch.gif
 
TryingToDo613
Junior tube assistant
Posts: 74
(5/25/05 10:49 pm)
Reply  Decoding
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 Hi Zachsdad. Your posts are always amazing, thanks. I'm going to try to translate and see if I have it.

Put a diode on each of the filiment leads coming out. The diodes terminate at a common point. That common point is joined to the back end of the coil and the minus (shorter) end of an led. The plus end is connected to a resistor that will vary brightness and other end of the led run back to the trip side of the coil. There is also a diode across the trips of the coil. At that plus end of the led I run the tip of the foot pedal. The sleeve is run back back to the ground of the center tap of the filiments.

Am I close? Do I use the little IN4001(??) diodes?

Also, can I use a 24vdc coil that the guy says trips at 6v? -613
 
zachsdad
Senior tube assistant
Posts: 182
(5/26/05 6:02 am)
Reply  Re: Decoding
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 The 1N4001 diodes will work. I doubt the relays will. In your explanation you have the LED reversed. It has to be forward biased. I left a component out of my drawing. Put a 4700 ufd
16V or higher electrolytic in the circuit with the positive side going to the commom point of the two diodes and the negative side going to ground. This filters the low voltage DC. A large capacitor is necessary to eliminate any hum from being injected into the audio circuits. Also I would probably stay with a 100 ohm resistor. This will keep the LED forward current in the 25mA neighborhood.
 
j allen shaw
I only work on Fender's
Posts: 699
(5/26/05 6:22 am)
Reply | Edit
  Re: To Bluesbear
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 bb,
Did you get a satisfactory answer to your question?

If not, try asking Ted Weber on his forum...he's really good about answering promptly.

www.webervst.com/vstbbs/bbs.html

Jeff
 
TryingToDo613
Junior tube assistant
Posts: 76
(5/26/05 7:52 am)
Reply  Forward march
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 Ok, thanks again. I will. I'll post results. -613
 
bluesbear
I only work on Fender's
Posts: 517
(5/26/05 3:27 pm)
Reply  Re: To Bluesbear
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 I appreciate everyone's help. I pulled the hot switch out of the amp! I ran out of space as this is a Princeton chassis. Also, everything being crammed together like this makes for some unbelieveable hum. I'll try these ideas out in a couple of weeks in one I'm making in a Komboking chassis. There'll be enough room in there!
Dave

Edited by: bluesbear at: 5/26/05 3:37 pm
 
 
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