Pedal Diode Protection & Battery Power Consumption?

[formerMember1]

After reading other posts and Geofx site I still ponder: :?:

1.Is it possible to use a diode to protect my RM clone, while still not decreasing battery power?
I don't have an adaptor hooked up to pedal and probably never will, I prefer the sound of batteries.

2.Since I am only going to use batteries for this pedal, do I have to protect pedal from touching a battery terminals backwards? (Could that really blow up a transistor or other parts, or do you have to literally hold the battery backwards to connectore for several seconds for the transistor to overheat?)

3.Usually a brand new battery tests 9.6 V or higher, so if there is only one way to insert a diode for protection and still decrease battery power, does that mean my battery will drain faster and I wont get as many hours out of each battery?

other  :?:
By installing a status LED in pedal, Does it really take that much more power than if no LED is used?It is noticeable?
If so,  if I make my LED less bright will it let my batteries last longer?
alot or not much?

replies appreciated

[MartyMart]

Ritchie, a "reverse protection" diode is exactly that, on a "normal"
negative ground circuit, you place the diode ( 1N4001 or similar) with the
cathode(-) towards the 9v supply  ( silver or black banded end ) and the
anode(+) towards ground.
For a "positive ground" circuit, just reverse that position so the banded
end connects with the now "positive" ground.
A very bright LED will drain a battery a bit quicker, the best way to do this
is to buy some "Ultra bright" LED's 3mm or 5mm, so you can run them with quite a large resistor from 9v  say 8k2 to 12 k
They will still "look bright" but will drain very little from the battery, as they are much more efficient.
If you use a standard red LED, you'll need it to recieve more current
to be bright enough  !

Marty.

[formerMember1]

thanks that cleared up the prob,
but one other question, or perhaps you did answer it and i don't realize it,

2.Since I am only going to use batteries for this pedal, do I have to protect pedal from touching a battery terminals backwards? (Could that really blow up a transistor or other parts, or do you have to literally hold the battery backwards to connector for several seconds for the transistor to overheat?)

thanks

ps: my LED's are fom the famous Small Bear,  :lol:
they say water clear high brightness, I assume these are the "efficient " ones you are talking about?
thanks again man

[Fret Wire]

For your other question, it depends on the ckt. Components don't have to overheat or blow up to be rendered useless by a momentarily reversed battery. Tantalum capacitors are extremely intolorant of reversed polarity. Some transistors can become very noisy from just one hit of reversed polarity. Some ckts can shrug off a momentary reverse with no ill effects. Depends on what's between the battery and any polarity sensitive components. As long as you're careful, you can get away without any protection on a battery only powered pedal. Many of the builds out there on popular sites don't have polarity protection in their layouts. It's still a good idea, a little more work for good insurance. With a power supply, I consider it mandatory, along with ps filtering.

[Sir H C]

To me, only op-amp circuits need the reverse polarity diode.  This is because the internal structures of ICs are such that when the supply is reversed often there are two diodes in series from rail to rail.  This will blow them up quickly.  With a transistor circuit like the RM, there is not as much problem with reverse battery, I forget the breakdowns on some of the diodes in those transistors but usually with the added resistors you don't have any problems.

[formerMember1]

thanks nice info there  :idea:

[Fret Wire]

To me, only op-amp circuits need the reverse polarity diode.  This is because the internal structures of ICs are such that when the supply is reversed often there are two diodes in series from rail to rail.  This will blow them up quickly.  With a transistor circuit like the RM, there is not as much problem with reverse battery, I forget the breakdowns on some of the diodes in those transistors but usually with the added resistors you don't have any problems.

In terms of immediate damage, maybe. A tantalum cap will be taken out quickly by reversed voltage, and bipolar transistors can become permanently hissy after just one hit, even though they will still function.

[formerMember1]

GEOFX SAYS:
The slightly slyer trick is to place a silicon diode cathode to + and anode to -. That means the diode does not conduct in normal operations, but shorts out the power when power is inadvertently reversed, protecting the circuit.


does that mean it won't take any power from battery?
also in a pnp wired pedal do i reverse what he said?
ex.cathode to - and anode to +.
anyway,does that mean i put that before or after a pulldown resistor, or where do i put it?


thankx, cuz um cunfuzed  :?

[Fret Wire]

GEOFX SAYS:
The slightly slyer trick is to place a silicon diode cathode to + and anode to -. That means the diode does not conduct in normal operations, but shorts out the power when power is inadvertently reversed, protecting the circuit.


does that mean it won't take any power from battery?

Nope, no voltage drop. And, just like RG says, if you reverse the polarity, the diode will stop current to the rest of the ckt.

also in a pnp wired pedal do i reverse what he said?
ex.cathode to - and anode to +.
Yes

anyway,does that mean i put that before or after a pulldown resistor, or where do i put it?

Neither. When you look at a ckt, you'll usually see connection pads for In, Out, Gnd, and Power, besides any pot connections. In (input) is where the audio signal comes into the ckt, that's where a pulldown resistor will go. Sometimes a pulldown is also used on the output also, but pulldowns are explained in the FAQ. Polarity protection goes where the Power (v+, -9v, +9v, etc.) comes into the ckt. After the battery or power supply, it will be the first component current hits, that way, no reversed power makes it into any part of the ckt.

Look at the Axis Face schematic. You're thinking of building one, right?
http://fuzzcentral.tripod.com/axisfacesi.html

The section on the extreme left is the input jack, which you have to remember, is stereo, and is also used to switch on power when your cord is plugged in. The stereo jack is connected to gnd, In, and V+. The ckt input is to the  right side of the jack, where you see a 1M pulldown resistor, then the Smooth pot. The power supply (+9v), is coming off the top of the jack. See a 100uf electro cap with the neg side to gnd, and a 1N4002 diode with the anode to gnd? That's it right there. Personally, in this particular ckt, I would switch the diode around with the capacitor, because I wouldn't want reversed polarity hitting any other component but the diode, especially any polarized components. The 100uf cap is for power supply filtering, always a good idea. This particular ckt is neg ground, for a pnp pos gnd ckt, you'd reverse the polarity of the diode and filtering cap.

Now, look at the Dist. + and MicroAmp schematics.
http://www.tonepad.com/getFile.asp?id=6

The Micro Amp has an inline diode, the type that will drop your battery voltage the amount of the diodes forward voltage rating. From there, the current goes to the voltage divider. On the Input section of the schematic, R1 is 22M plenty enough for pop protection.

Now look at the Dist. + schematic. At the V+ section, you see +9v coming off the input jack. No diode or filtering cap. Current goes straight to the voltage divider. Look at the input section, no pulldown resistor going to gnd. You would insert one between the input and the first capacitor (C1). Say you bought a Dist. + board from Tonepad (great pcb layouts), and you want polarity protection, power supply filtering, and a pulldown resistor. You can add them in your offboard wiring no problem.

Go over the FAQ and beginner section again to make sure you got it down as far as jack switching goes, and understanding the various sections that most ckts have. Check some schematics on Tonepad and General Guitar Gadgets and you'll recognize the input, output, power, and other sections of the various ckts.

[Processaurus]

Since you're using strictly battery power, the "slyer trick" of using shunt diode protection from Geofex will work well.  Since a diode is like a one way street for current, you place it across your power and ground rails in a way that it only conducts current when a battery is put in wrong.  It just shorts out the battery, saving your circuit.  Since its impossible to put a 9v battery in a clip wrong except by holding it, you may decide you are responsible enough to never put it in wrong (I know better than to do this but have occasionally tried to put batteries in like a cave man and connect them wrong momentarily saying "uuggh, no worky?").  If want your pedal to be bullet proof and want to try the diode protection that shorts the battery, get a beefy power diode, like a 1n4001, that can handle a lot of current.  For your positive ground PNP Rangemaster, put the side of the diode with the mark (the cathode) to ground and the anode to power (which in this pedal's case is the minus side of the battery).  That way it never conducts during normal operation, only when the battery is placed on the contacts wrong.

[formerMember1]

thanks fretwire and processaurs,
ya really explained it well,
even though i most likely won't connect the battery backwards i will install the protection diode to learn from it, so when i do build an axis face i will have the expeirence,
thanks again for the help,