Search found 1497 matches

by dyarker
Fri Nov 16, 2018 12:08 pm
Forum: General Discussion
Topic: Forum Update! Secure!
Replies: 14
Views: 336

Re: Forum Update! Secure!

((even the spammers were encrypted while created user accounts :grin: , (different protection called for)))
by dyarker
Fri Nov 16, 2018 12:04 pm
Forum: General Discussion
Topic: diamond bangles
Replies: 2
Views: 9

Re: diamond bangles

reported to admin this mornig
by dyarker
Fri Nov 16, 2018 12:04 pm
Forum: General Discussion
Topic: Reliable online help
Replies: 2
Views: 9

Re: Reliable online help

reported to admin this morning
by dyarker
Fri Nov 16, 2018 4:16 am
Forum: General Discussion
Topic: How to select the Gate Drive Resistor
Replies: 1
Views: 12

Re: How to select the Gate Drive Resistor

What is your major?
by dyarker
Thu Nov 08, 2018 12:33 pm
Forum: General Discussion
Topic: Microphone in a bubble...
Replies: 7
Views: 158

Re: Microphone in a bubble...

Oh yeah! How waterproof? Rain/spit/sweat? Or, submerged? (and depth?)
by dyarker
Wed Nov 07, 2018 3:12 pm
Forum: General Discussion
Topic: Microphone in a bubble...
Replies: 7
Views: 158

Re: Microphone in a bubble...

Not a truely rigid bubble. Sound (higher and lower preasure) on the outside needs to deform/flex to make higher and lower presure in the air inside.

Same for "Gummy Bear" soft, except sound is absorbed, nothing inside to vibrate the mic element.
by dyarker
Wed Nov 07, 2018 7:09 am
Forum: General Discussion
Topic: How select the Commonly Used Electronic Components
Replies: 6
Views: 125

Re: How select the Commonly Used Electronic Components

The pick of a part usually narrows down to one or two when you "do the numbers". Following your power supply cap example - You need the minimum voltage the load can run with, and maximum current it will draw. The peak of the maximum rectified voltage minus then minimum the load can use is the supply...
by dyarker
Mon Nov 05, 2018 10:57 am
Forum: General Discussion
Topic: Lithium Ion charger hack..
Replies: 7
Views: 270

Re: Lithium Ion charger hack..

Wiper of a pot to IC temperature measuring pin. Ends of pot to Vcc and common. Adjust pot till IC cuts the charging current. Measure voltage at wiper. Warm NTC to temperature where cell charging should stop. Measure resistance of NTC. A touch of algebra (or longer way with Ohm's Law) gives resistanc...
by dyarker
Thu Nov 01, 2018 1:32 pm
Forum: Robotics
Topic: How to extract the pulsed output from Servo motor and send to wireless converters
Replies: 1
Views: 129

Re: How to extract the pulsed output from Servo motor and send to wireless converters

Are you talking about servos that set the position of the output shaft based on pulse width of the input pulses? What does the wireless analog to digital converter (ADC) have to do with pulse width control? ADCs convert a level to a digital number. The pulses to a servo are at ON level or OFF level;...
by dyarker
Tue Oct 30, 2018 3:05 pm
Forum: General Discussion
Topic: Lithium Ion charger hack..
Replies: 7
Views: 270

Re: Lithium Ion charger hack..

Two components and three connections complicated????? The NTC is in physical contact with cells. It's resistance changes with temperature OF THE CELLS. The junction of NTC and a fixed resistor is wired to (pin 1?) of the IC. The IC circuitry measures the voltage to control the charge current. The ot...
by dyarker
Wed Oct 24, 2018 7:30 am
Forum: General Discussion
Topic: Need help with a circuit again
Replies: 29
Views: 719

Re: Need help with a circuit again

sure! the bulbs will be too much current for 2N3906s, so use LEDs and 1K resistors.
by dyarker
Wed Oct 24, 2018 4:17 am
Forum: General Discussion
Topic: Need help with a circuit again
Replies: 29
Views: 719

Re: Need help with a circuit again

Schmidt2LEDs2.png
Last night 20 logins, nothing; today 2 like you said.
by dyarker
Tue Oct 23, 2018 6:22 pm
Forum: General Discussion
Topic: Need help with a circuit again
Replies: 29
Views: 719

Re: Need help with a circuit again

try to attach schematic, get logged out
by dyarker
Tue Oct 23, 2018 3:22 pm
Forum: General Discussion
Topic: Need help with a circuit again
Replies: 29
Views: 719

Re: Need help with a circuit again

Without R3 the circuit is not a schmitt trigger anymore. The Q1 base resistance to negative supply is like 1 or 2 Ohms (bad!). With R3 the base resistance is like 50K to 100K (no burnt pots). R3 being "shared" with Q2 causes the "snappy" switch between which transistor is on. It is better to put ori...
by dyarker
Mon Oct 22, 2018 7:44 am
Forum: General Discussion
Topic: Need help with a circuit again
Replies: 29
Views: 719

Re: Need help with a circuit again

Looking at it again -

What else have you done?

R3 times the gain of Q1 should have prevented pot burn-out.

What colors are the bands on R3?