BARACUDA-Legend-1

[kt315]

about coil for bara i told scaled http://www.geotech1.com/forums/showt...l-for-baracuda

George mod is not about sensitivyty and the depth =) leave all as-is.
do not do the mod now.

[BKY1337]

Ok, can you tell me what this mod does? Will i have more depht or more sensitivity?

And can you tell me pls which coil i should use? Wire thickness and uH.
Do you think 0,5mm wire is good and 330 uH with graphite shield.

[kt315]

Ok , i will take a look at it but i already have everything soldered.

.

ok, you can use the board as-is. but if you meet a problem with 40106 burnt you know a way.

[kt315]

you have to cut one trace and do one connection, on bottom side.

[BKY1337]

Ok , i will take a look at it but i already have everything soldered.

I have used very small resistors too , the tayda ones are only the half in size of regular transistors.
And im not very satisfied with the accuracy of them . I think they are only 2% not 1%.

[kt315]

i have 9pcs boards not sold... i correct a layout only after full realisation.
mod is simple to do.
take George's schematic and mine, compare, and you will see differency. look on resistors on 40106.

It's both. The Geotech Baracuda REV-A (when it's finally released as a PCB) will be a corrected and slightly modified version of the original Baracuda. If anyone wants to patch their original Baracuda, I can post a list of changes required. These changes essentially consist of connecting the pull-up resistors to 0v instead of +5V, and some modifications to the power supply smoothing capacitor connections, plus one additional capacitor and a value change. The offset null on the NE5534 can stay as it is. A final [optional] update is to unplug the 7660S, and plug in an LT1054.

I'll create a change document later.

[Andi68]

Is it possible to use very small resistors, dm- 1.6mm, l- 3,2mm?
I take it from an old TV board.

[BKY1337]

I dont know Georges mod. I have bought LED Bezels and i want to have a LED in the front of my Housing where the Pots are.

Is this mod already in my bom and gerber files?

BTW: Which coil is the best for the Barracuda Legend REV-B?

I want to build a 27cm coil. I have 0.25mm enamelled wire. I have heard that 0.5mm is better.
How much uH is best fo this metal detector?

[kt315]

do not looked the schematic. you waste a time. no differency what LED you use.
better do George's mod and set the resistors from his schematic.
i corrected BOM included the mod.

[BKY1337]

I haven't build the barracuda yet , i only looked at the schematic because im building the board.

I want to use my 3.2 - 3.3V LED instead of a red one with a forward voltage of 1.9v which.

[kt315]

i didn't knew that i have 1,9 Volts at the place where the LED is

you can not measure a voltage on LED be cause it is AC voltage, not DC. 600PPS. or 600Hz.
you must look the impulses by o-scope.

ie LED is lighten in impulse mode, NOT in DC.

[BKY1337]

Yes , but i didn't knew that i have 1,9 Volts at the place where the LED is, thats why i asked.

I need to change the 100R with a 87R or the 33R with a 37R to achieve 3.3 Volts where my LED is.

Does this Change affect other parts in the circuit?

[waltr]

Damn, i have only bought two different LEDs , white and blue.

Forward Voltage is like i said 3.2 - 3.4Volts.

Don't feel too bad. I worked with a Masters degree'd engineer that did the same thing. Tried running a Blue LED (Vf ~4V) from 3.3V. It did not light up.

[BKY1337]

Depends on which LED and its V forward spec. Most IR, RED, Green, Yellow LEDs have a Vf of around 1.4V so 3.3 will work.
However, Blue, White and UV LEDs have a Vf of around 4V (check spec) so will not work with 3.3V.

Damn, i have only bought two different LEDs , white and blue.

Forward Voltage is like i said 3.2 - 3.4Volts.

[waltr]

Can i use the LEDs from Tayda with 3,3V?

Depends on which LED and its V forward spec. Most IR, RED, Green, Yellow LEDs have a Vf of around 1.4V so 3.3 will work.
However, Blue, White and UV LEDs have a Vf of around 4V (check spec) so will not work with 3.3V.

The current of the LED must be limited, which is more important than the voltage- look for LED-Rechner

Exactly- Google biasing LEDs and read the Vf spec of the LED.
The supply Voltage most be higher than the LED's Vf and then CURRENT limited (set) to obtain the desired brightness AND not over current the LED.

Measure the Voltage Drop across the resistor to calculate the
LED current using Ohm's Law.

The specs of my LED are 3.2 - 3.4 V and 20mA.

Is that the Vf spec? If so then probably will not work from 3.3V. The Voltage must be higher than Vf so there is a Voltage drop across the current limiting resistor.
Otherwise one needs to use a Constant Current Source (or Sink) circuit to set the LED current.
The 20mA spec is the MAXIMUM allowed current. Much lower current is commonly used with a minor decrease in brightness.
I typically start at around 5mA for a 20mA max spec.