What is a custom buffer? Is it really necessary? By a A/D voltmeter I gather you mean one of the voltmeters that produces a graph so I can read off the "big" peak and get the voltage. Is making the custom buffer hard?
using a current to measure a time interval
Dec 01, 2005
27 Replies
. | | /STOP| | | | . Vbatt | | | \\| | | . | | | | 2N3904|---|--[10K]------' . .-----------+-------. | | UNILAB| |--+-----|--->TO FF CLR . | | | 100n -------555 | ------- | . | | | | | | | . '----+------+-------+-------|------------------------' . | 1N914 | . '-+---|
Add a diode in that FF CLR ckt like so: View in a fixed-width font such as Courier.
. . . . . .-----------. . | | 74HC74 . | ---------- . | | PR | . | |Q D |-----------------. . | | | | . | | | | . | | CLK |---. | . | |_ | | | . | .---|Q | | | . | | | | | | . | | | CLR | | | . | | ---------- | | . | | | | | . .--[10K]---|--|---------+--|>|---|-----. . | | | | | |G2 >--+-|--/ /___/ | | . | | | | .-/ /___/ | | | . | C1 | | | | | | | . | .----------||------+ | | | | | | . | | 220n | | | | | | | . | | | | | | | | | . | | .----[100K]----+ | | | | | | . | | | | | | | | | | . | | | _ | | | '-------------|-------+---' | . | | | /| | | | | | | . | | [5M] | | | | | | . | | /| BREAK | | | | | | . | | | ADJ | | | | | | . | | | | | | | | | . | | | ---------U1 | ---------U2 | | . | | | | VCC RST | | | VCC/RST | | | . | '---+-----. | | | | | | | . | | .-|THRESH OUT|-+-[150K]+--|THRESH OUT|-' | . .-------+--[100]-+-+ | | | | | | . | | | '-|TRIG | +--|TRIG | | . CON-o | | | | C2| | | | . TACT | | | GND | === | GND | | . o | | --------555 100n -------555 | . | | | | | | | . '---+---------------------+---------------+-------+com | . | | | . | 1N914A ------- | | . '----------|>|---. | START|-------. | | . | | /STOP| | | | . Vbatt | | | \\| | | . | | | | 2N3904|---|--[10K]------' . .-----------+-------. | | UNILAB| |--+-----|-->TO FF CLR . | | | 100n -------555 | ------- | . | | | | | | | . '----+------+-------+-------|------------------------' . | 1N914 | . '-+---|
I mean a amplifier that has such a high input impedance (like 1000 Megs) that it will not contribute to the leakage of charge from the capacitor. The input of a typical A/D may not be good enough in that regard.
Actually, I meant a plug-in board on a PC that makes it possible for software to capture the voltage.
No, a single-stage op-amp will do, if the op-amp is selected for ultra-low input bias current, like most FET-input op-amps.
-Robert Scott Ypsilanti, Michigan
As I understand it, he has two inputs on his timer, a start and a stop. Assuming a + level activates a timer input, and that he must use that timer:
+---> timer start | | +V ---------+--------+---------------+----+ | | | | | [R] | | [R] | | | \\ | | | \\ +-------|+ \\ | +-------|+ \\ | | }---+ | | | }--- timer stop [R] +---|- / | +---|- / | | | / | | | / Contact -- | --+ | | [R] | | | | | | | Gnd | Gnd | Gnd Gnd | | +----------------+Contact | Start | Stop ====================== - | + | - + | - | +
I don't know if his timer will start/stop in response to bounce - I view it (a la your elegant R/C solution) that total collision time is literally when the contacts are touching, so that the periods when they do not touch due to bouncing during the colision event should not be counted.
If he *must* use that specific timer, is there a better way?
Ed
Don't waste your time- once the OP sees more than two or three components, like a switch and a battery , he runs off in terror...
There will be no uncomplicated circuit solution for your problem- so you will have to find assistance locally.
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