Quick troubleshooting question for gravitation reverb

steviejr92

Authorized Vendor
Hey guys your friendly neighborhood noob here once again. I just have a quick question I’m measuring the forward voltage on my diode it’s a 1N5817 Schottky diode I read that it should have a forward voltage of .2 v when I measure I get .167 is this ok?
 
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AFAIK a 5817 is a 5817 is a 5817, so you should be good to go.

I don’t think a fraction of difference between your reading and the 0.2V will have an impact. If in doubt, socket and see so you can swap it out if there are issues.
 
Hey guys your friendly neighborhood noob here once again. I just have a quick question I’m measuring the forward voltage on my diode it’s a 1N5817 Schottky diode I read that it should have a forward voltage of .2 v when I measure I get .167 is this ok?
I’ve noticed that depending on the make they will vary. For instance, I bought a big pack of 1n5817’s off Amazon in a pinch made by some anonymous Asian mfgr and they all measure consistently low on the Vf compared to the ones I get from stomp box parts. But for the majority of the use cases for DIY board they’re employed as reverse voltage protection and I can’t see that it makes any difference.
 
the rest of my resistors should come in I’ve already soldered the rest just missing a 470r resistor in there I’ve been checking continuity between joints and I’ve been getting readings everywhere so I think I’m on the right track lol will keep you guys updated further today!
 
Apparently …

The Schottky Diode is another type of semiconductor diode which can be used in a variety of wave shaping, switching and rectification applications the same as any other junction diode. The main advantage is that the forward voltage drop of a Schottky Diode is substantially less than the 0.7 volts of the conventional silicon pn-junction diode.

Schottky diodes have many useful applications from rectification, signal conditioning and switching, through to TTL and CMOS logic gates due mainly to their low power and fast switching speeds.
 
the rest of my resistors should come in I’ve already soldered the rest just missing a 470r resistor in there I’ve been checking continuity between joints and I’ve been getting readings everywhere so I think I’m on the right track lol will keep you guys updated further today!
Yeah, it’ll be good to know that you (and your build, of course) are ok 😎
 
Apparently …

The Schottky Diode is another type of semiconductor diode which can be used in a variety of wave shaping, switching and rectification applications the same as any other junction diode. The main advantage is that the forward voltage drop of a Schottky Diode is substantially less than the 0.7 volts of the conventional silicon pn-junction diode.

Schottky diodes have many useful applications from rectification, signal conditioning and switching, through to TTL and CMOS logic gates due mainly to their low power and fast switching speeds.
So in this situation lower power means faster switching speeds and overall better application for power than silicon?
 
So in this situation lower power means faster switching speeds and overall better application for power than silicon?
Not sure one can go that far. Seems @MichaelW has it correct; they provide reverse polarity protection and less of a voltage drop than the 4001s. How I read it as that you lose less voltage to the diode drop thereby, which matters, I guess, when you’ve only got 9V to begin with.

I’ll show myself out 😊
 
You’re measurement seems fine to me.

I think the main reason pedalpcb uses schottky here is to minimize the voltage lost from 9V since it’s in a series configuration. Many pedals have a 1n4001 from power to ground. The advantage is that there is no voltage drop in this configuration. The problem is that if you apply reverse power, it fries the diode, and the pedal doesn’t function till you replace it. It’s an easy fix and saves the rest of the circuit, but the schottky in series is great because if you apply reverse power, nothing fries. The tiny 0.2v drop in power is totally worth the better protection, in my opinion.


Diodes (including LEDs) do not just have a perfect single forward voltage for all circumstances, rather the forward voltage changes depending on the current passing through the diode. Here’s a chart from the 1n5817 datasheet. It shows about 0.2v at 100mA, and that’s as low as the chart goes. The gravitation would pull lower than 100mA total through the pedal, so it actually makes sense that you measured a little lower than 0.2V if you measured in circuit. If you measure out of circuit with a DMM, it really depends on what current the DMM is pumping through the diode to measure it. And for sure there can be variation from part to part.
 

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You’re measurement seems fine to me.

I think the main reason pedalpcb uses schottky here is to minimize the voltage lost from 9V since it’s in a series configuration. Many pedals have a 1n4001 from power to ground. The advantage is that there is no voltage drop in this configuration. The problem is that if you apply reverse power, it fries the diode, and the pedal doesn’t function till you replace it. It’s an easy fix and saves the rest of the circuit, but the schottky in series is great because if you apply reverse power, nothing fries. The tiny 0.2v drop in power is totally worth the better protection, in my opinion.


Diodes (including LEDs) do not just have a perfect single forward voltage for all circumstances, rather the forward voltage changes depending on the current passing through the diode. Here’s a chart from the 1n5817 datasheet. It shows about 0.2v at 100mA, and that’s as low as the chart goes. The gravitation would pull lower than 100mA total through the pedal, so it actually makes sense that you measured a little lower than 0.2V if you measured in circuit. If you measure out of circuit with a DMM, it really depends on what current the DMM is pumping through the diode to measure it. And for sure there can be variation from part to part.
And there’s the authoritative answer for your reference. Hadn’t thought about the series wiring but did manage once upon a time to blow up two 10R resistors by reverse-connecting a module power supply. Quite spectacular; they melted in a couple of seconds and emitted wonderful smoke.
 
You’re measurement seems fine to me.

I think the main reason pedalpcb uses schottky here is to minimize the voltage lost from 9V since it’s in a series configuration. Many pedals have a 1n4001 from power to ground. The advantage is that there is no voltage drop in this configuration. The problem is that if you apply reverse power, it fries the diode, and the pedal doesn’t function till you replace it. It’s an easy fix and saves the rest of the circuit, but the schottky in series is great because if you apply reverse power, nothing fries. The tiny 0.2v drop in power is totally worth the better protection, in my opinion.


Diodes (including LEDs) do not just have a perfect single forward voltage for all circumstances, rather the forward voltage changes depending on the current passing through the diode. Here’s a chart from the 1n5817 datasheet. It shows about 0.2v at 100mA, and that’s as low as the chart goes. The gravitation would pull lower than 100mA total through the pedal, so it actually makes sense that you measured a little lower than 0.2V if you measured in circuit. If you measure out of circuit with a DMM, it really depends on what current the DMM is pumping through the diode to measure it. And for sure there can be variation from part to part.T
This is really good to know!
 
And there’s the authoritative answer for your reference. Hadn’t thought about the series wiring but did manage once upon a time to blow up two 10R resistors by reverse-connecting a module power supply. Quite spectacular; they melted in a couple of seconds and emitted wonderful smoke.
I’m going to take note on that I’ve smelled enough burnt circuit board with the last gravitation board to stay away 🤣
 
And there’s the authoritative answer for your reference. Hadn’t thought about the series wiring but did manage once upon a time to blow up two 10R resistors by reverse-connecting a module power supply. Quite spectacular; they melted in a couple of seconds and emitted wonderful smoke.
Do you mean reverse polarity ? I don't think you can burn a resistor that way...
 
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