circuit challenge

The changes in blink rate don't have to be discrete, they can be continuous as well.

On a sunny day (Tue, 8 Jul 2014 03:00:01 -0400 (EDT)) it happened bitrex wrote in :

With all respect, I think it makes little sense to ask somebody to calculate the longest distance between 2 points, unless you get payed for the time and a bad product. A PIC 12F can do this without ANY external components, with great precision.

V to F converter + missing pulse detector

Tim

-- Seven Transistor Labs Electrical Engineering Consultation Website:

So boring!

On a sunny day (Tue, 8 Jul 2014 05:11:58 -0400 (EDT)) it happened bitrex wrote in :

OK design a manned mars lander.

So the input Vs switch a couple of trs; one changes the R or C in an RC-opa oscillator, the other turns the opamp on all the time. Not really rocket science.

NT

Voltage to frequency converter.... done.

George H. (if not a discrete IC then a VCO -> current into a cap -> triangle wave.)

If the blink rates, duty cycle, thresholds and linearity are not critical why not just take a classic two transistor astable multivibrator and kludge in a resistor from Vin to base of one of the transistors?

If 50% duty cycle wanted then use another R to the other transistor too. To get the steady ON led when Vin>5V may need a third transitor with appropriate divider at base.

What supply voltage does this challenge circuit have available, 3.3V,

Do you want to add restrictions to the challenge like no ICs, or no large value capacitors, or only parts available in 1975, or no more than twelve parts etc etc?

piglet

A CMOS 555 with an RC lowpass between the output and the trigger & threshold pins, plus three resistors on the modulation pin. A D flip flop following will give you a 50% duty cycle if you need it.

Cheers

Phil Hobbs

And you can only use 555 chips.

Soemthing like this

VCC VCC VCC + + ___ + +---------------------------+ +|-|___|+ | | .-. | | | |< | | | | | V +------ -| | | | 1K .-----------------. - | |\ | VCC '-' | RES |-+ | +--+ + +------| | | | | .-. | | | .-. | | | | | | | | .-. | | 100K| | | | | | | '-' | | | '-' | | +----+- | | .-. | '-' |+ |+ | | | | | --- --- | | | | GND +---+ --- --- | | '-' | | | | | | | _R1 |/ | |/ | | | -------+- -|___|- -+-- -| +--| === | | | |> |> GND | | .-. | | | | R2 | | === === | | | | GND GND | | '-' '-----------------' | | === === GND GND

R1/R2 set threshold of first transition Vcc - Vbe is second transition

Block is a 555

"picky picky", :^) Well at 20V it would be 20Hz which would look like it was continuous.

George H.

Jan Panteltje wrote in news:lpga2h$nm6$ snipped-for-privacy@news.albasani.net:

Can be considered overkill. A six pins PIC10F220 will do. I'd advise to use a series resistor for the LED. Boring? Sure. After all it's not a real challenge. I don't expect anyone to build a circuit like this unless he (she?) has a use for it. (Nevertheless, if someone needs it, I can build a prototype for a reasonable price :)

petrus bitbyter

The strength to weight ratio is too low to be practical.

As long as a supply of oxygen is allowed, they probably wouldn't be a bad propellant though.

:^)

Tim

o +12 V | | +------------------+ | | +-----+ | | | / R1 / Q1 / R2 \ Vin o--+--->|--->|--->|--->|--->|---| \ / | D1 D2 D3 D4 D5 \ / | | | | | | +-----+ | | | | +--->|------------------------+ | D6 | | / \ M1 /U\ Disc V LED1 ( )====( ) - \_/ \_/ | | | | | Gnd o--------------------------------+------------------+

D1-D5: 1N4001 D6: Some kind of small Schottky diode with low forward drop Q1: NPN, to suit current requirements of M1 M1: Small DC motor, probably about 6-8 V nominal R1: To suit current requirements of LED1 R2: Just enough to supply about 0.3 V to M1 LED1: LED of desired color, located behind disc Disc: Slotted disc attached to M1 shaft

At less than about 0.3 Vin, R2 supplies M1. The slotted disk occludes LED1 at 1 Hz.

From about 0.3 to 5.0 Vin, the input supplies M1 directly. Increasing voltages increase the RPM of M1, thereby increasing the apparent blink rate of LED1.

At 5.0 and above Vin, Q1 turns on, providing a high voltage to M1, causing it to spin so fast that LED1 appears to be continuously on.

Matt Roberds

- YD.

On a sunny day (08 Jul 2014 20:33:24 GMT) it happened petrus bitbyter wrote in :

Yes, I was planning on leaving the LED series resistor out and doing it this way: Use input pullup, connect LED to input. Modern high efficiency LEDs will work on a few hundred uA. Then if the LED needs to be off, reconfigure pin as output and logic level zero. Now I want half the reasonable price ;-)

The biggest problem will be the unspecified > 5 V. I think 5.1 will meet the spec, but he could be using 2 MV or more.

Experiment will show if we actually need a decoupling cap, or just use a good quality battery, The thing will have to run at 5.2 V or so to allow sufficient input range for comparators or ADC.

Analog is failry easy to, I'd use a quad single supply opamp,