RE: Help With Electric Project for Alzhimerz
March 13, 2017 at 8:30 pm
(This post was last modified: March 13, 2017 at 8:52 pm by AFTT47.)
Jenny, my background is in electronics.
I don't know what website you were looking at to calculate capacitance values to give you 40 MHz in an oscillator but there are several issues:
At that frequency, it's going to take more than just plugging the right parts into a breadboard. Stray inductance from wires and leads and stray capacitance from a number of sources can cause problems. I'm not confident that you and hubby could build a 40 MHz oscillator even if you had a schematic and all the parts in front of you.
Whatever oscillator you use must either directly output enough current to drive the LED or it must be used to switch a transistor off and on which will drive the LED.
I'm not sure if just any LED can be switched at that frequency. Forty MHz is well into the radio spectrum, above the HF band. Driving one at that rate is unusual to say the least.
You should also be aware that even at a few kilohertz, the LED will appear to be on steadily with no appearance of flashing at all. This is because of a phenomena called persistence of vision. Because of that, I don't see how the brain could get a 40 MHz signal from your eye. I don't believe the human eye could differentiate from 3000 Hz and 40 MHz. Sounds very fishy to me.
Here is a complete 40 MHz oscillator from Mouser Electronics for $1.76 in single quantities. This is pretty much plug and play. It needs to be powered by 5 volts. It says it is rated at 45 milliamps which is plenty of current to drive an LED. You would need a current limiting resistor so as not to fry the LED. To calculate the value, divide 5 (the voltage of the output) by whatever the current rating of the LED is. For example, an LED rated at 5 milliamps would need a 1000 ohm resistor (5/.005 = 1000).
I don't know what website you were looking at to calculate capacitance values to give you 40 MHz in an oscillator but there are several issues:
At that frequency, it's going to take more than just plugging the right parts into a breadboard. Stray inductance from wires and leads and stray capacitance from a number of sources can cause problems. I'm not confident that you and hubby could build a 40 MHz oscillator even if you had a schematic and all the parts in front of you.
Whatever oscillator you use must either directly output enough current to drive the LED or it must be used to switch a transistor off and on which will drive the LED.
I'm not sure if just any LED can be switched at that frequency. Forty MHz is well into the radio spectrum, above the HF band. Driving one at that rate is unusual to say the least.
You should also be aware that even at a few kilohertz, the LED will appear to be on steadily with no appearance of flashing at all. This is because of a phenomena called persistence of vision. Because of that, I don't see how the brain could get a 40 MHz signal from your eye. I don't believe the human eye could differentiate from 3000 Hz and 40 MHz. Sounds very fishy to me.
Here is a complete 40 MHz oscillator from Mouser Electronics for $1.76 in single quantities. This is pretty much plug and play. It needs to be powered by 5 volts. It says it is rated at 45 milliamps which is plenty of current to drive an LED. You would need a current limiting resistor so as not to fry the LED. To calculate the value, divide 5 (the voltage of the output) by whatever the current rating of the LED is. For example, an LED rated at 5 milliamps would need a 1000 ohm resistor (5/.005 = 1000).
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former.
Albert Einstein
Albert Einstein
