If this was discussed, then I missed it.
What's going on with the transition from 4001 to 5817 as the power protect diode?
Somebody can correct me, but I think it's because you can put the 5817 in series with the power rail and suffer almost no voltage drop.
4001 is used in a "crowbar" formation, where it goes between +9V and ground, with the cathode pointed toward +9V. It shunts the voltage if you plug in the wrong polarity power supply -- which protects the components but will create a situation where your power supply can supply enough current to eventually (and by "eventually" I mean "very quickly in real life") destroy the diode, creating a dead short to ground. However, a battery can't supply enough current to kill a 4001, so it works to protect the components if you momentarily connect the battery the wrong way around. The worst that happens then is you drain the battery a little.
Using a 1n5817 in series with the power supply means that if you connect the wrong polarity of power supply, you will simply get no voltage passing, because the diode will block it completely. The price you pay is the loss of a trivial amount of voltage (0.2V in this case).
When people were powering their effects mostly with batteries, using the crowbar method with the 4001 was perfectly acceptable because it did exactly what was needed and sacrificed no voltage, which could matter when the battery became particularly drained. Now, though, almost no one uses batteries, especially in DIY pedals, so it's better to just use the way that won't kill a pedal.
Quote from: midwayfair on February 05, 2015, 06:30:55 PM
4001 is used in a "crowbar" formation, where it goes between +9V and ground, with the cathode pointed toward +9V. It shunts the voltage if you plug in the wrong polarity power supply -- which protects the components but will create a situation where your power supply can supply enough current to eventually (and by "eventually" I mean "very quickly in real life") destroy the diode, creating a dead short to ground. However, a battery can't supply enough current to kill a 4001, so it works to protect the components if you momentarily connect the battery the wrong way around. The worst that happens then is you drain the battery a little.
Using a 1n5817 in series with the power supply means that if you connect the wrong polarity of power supply, you will simply get no voltage passing, because the diode will block it completely. The price you pay is the loss of a trivial amount of voltage (0.2V in this case).
When people were powering their effects mostly with batteries, using the crowbar method with the 4001 was perfectly acceptable because it did exactly what was needed and sacrificed no voltage, which could matter when the battery became particularly drained. Now, though, almost no one uses batteries, especially in DIY pedals, so it's better to just use the way that won't kill a pedal.
Why the switch to the 5817 though? Just lower forward voltage than the 4001?
Quote from: mandrewbot3k on February 05, 2015, 06:37:17 PM
Why the switch to the 5817 though? Just lower forward voltage than the 4001?
Yes, and because they're different types of diodes with different purposes.
Quote from: midwayfair on February 05, 2015, 07:17:33 PM
Quote from: mandrewbot3k on February 05, 2015, 06:37:17 PM
Why the switch to the 5817 though? Just lower forward voltage than the 4001?
Yes, and because they're different types of diodes with different purposes.
I guess I meant, why wouldnt the 4001 work in series? just too big of a Vdrop?
Quote from: mandrewbot3k on February 05, 2015, 08:03:28 PM
Quote from: midwayfair on February 05, 2015, 07:17:33 PM
Quote from: mandrewbot3k on February 05, 2015, 06:37:17 PM
Why the switch to the 5817 though? Just lower forward voltage than the 4001?
Yes, and because they're different types of diodes with different purposes.
I guess I meant, why wouldnt the 4001 work in series? just too big of a Vdrop?
Exactly. 1n4xxx have a 1.0V voltage drop.
Thanks guys.
Made this video about a year ago on the topic. pros and cons to both methods I guess:
Link: http://www.youtube.com/watch?v=V-OYXdKMG8s
Quote from: chromesphere on February 06, 2015, 01:33:26 AM
Made this video about a year ago on the topic. pros and cons to both methods I guess:
Link: http://www.youtube.com/watch?v=V-OYXdKMG8s
Edit: ^ Those were thumbs up on my iPad. Apparently that didnt come across that way on the PC.
lol no worries mate, i saw the thumps up though :D
Quote from: midwayfair on February 05, 2015, 06:30:55 PM
4001 is used in a "crowbar" formation, where it goes between +9V and ground, with the cathode pointed toward +9V. It shunts the voltage if you plug in the wrong polarity power supply -- which protects the components but will create a situation where your power supply can supply enough current to eventually (and by "eventually" I mean "very quickly in real life") destroy the diode, creating a dead short to ground. However, a battery can't supply enough current to kill a 4001, so it works to protect the components if you momentarily connect the battery the wrong way around. The worst that happens then is you drain the battery a little.
Using a 1n5817 in series with the power supply means that if you connect the wrong polarity of power supply, you will simply get no voltage passing, because the diode will block it completely. The price you pay is the loss of a trivial amount of voltage (0.2V in this case).
When people were powering their effects mostly with batteries, using the crowbar method with the 4001 was perfectly acceptable because it did exactly what was needed and sacrificed no voltage, which could matter when the battery became particularly drained. Now, though, almost no one uses batteries, especially in DIY pedals, so it's better to just use the way that won't kill a pedal.
Years ago, but thanks!