| Electronics > Beginners |
| SMD or THH or dead bug ? for Mr.Carlson's Super Probe ? |
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| lordvader88:
I built this on a breadboard and used some coax cable, and it works great. He says to use a 'super bright' green LED. What does he mean by that ? I have average grn LED w/ Vf=1.8V or whatever. I used a blue 3V LED, but never changed anything else. I have a little metal case, that can fit about a 2-3cm wide prototype board. I salvaged most the SMD parts I would need, even the caps For dead-bugging, I'm brand new, using a knife to cut isolated islands, and I have no glue. I wondering what would be cleaner, to make a dead-bug version on a gnd plane. OORRR to use perf.board and make a mix if smd/THH ?? I'm sure I won't notice the difference, but which is better , both would be pretty small? What about TO92 BJTs vs sot23? I could either in any prototype.. And would a USB cable make a good cable to go from the probe-handle to the box w/ the audio and knobs ? Or does that have to be coax |
| Bud:
I think the use of a superbright LED is to save battery power. The LED appears to be powered via a 1K resistor and transistor from 5V supply, which would produce 2.5..3mA current through the LED. This would be too little current for normal LED (10-20mA) but a superbright LED would work at normal brightness with this small current. |
| lordvader88:
what would the voltage drop be ? I haven't figured out how the settings, and inputs, affect the LED, it's works enough tho. Plus so far I mainly used it UN-sheilded. I just salvaged a SMD LM4808LowVoltageHighPowerAudioPowerAmplifier, which is also tated for under 6V, so it's probably like Mr.C's chip. Right now I'm just using a LM386. |
| bson:
A green superbright will light up enough for indicator use at ~50µA. Also called low-current or ultrabright LEDs. |
| Dacke:
I just used a cut piece of protoboard and mostly through hole, a couple things were SMD, and a LED I found in my LED bin. Took a few tries to find an LED that would work with that low current. Also using a 9V battery with a 7805 instead of the 4 AAs because they wont fit in the probe body I have. Most of these components I already had. I'm not using the amplifier box he used, as this probe is used directly with a signal tracer. The 7805 is not really necessary, but there just in case I modify this to use a different power source and I have tons of them anyway. The probe works, I just have to finish the probe body, it's just a piece of polycarbonate pipe with copper tape around it and vinyl end caps. If you're looking for the coax he used for the probe tip, I believe it's RG142. |
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