Bill Marsden's Test probe?

Thread Starter

bundick

Joined Dec 19, 2007
97
Bill put up this test probe on another thread. If the frequency we are looking at is so high it makes the LED glow as if your looking at a steady state, is there a little discrimination circuit we could adapt so the Cmos input would see only every 4th or 100th pulse?
Cmos test probe.gif
 

SgtWookie

Joined Jul 17, 2007
22,230
Here's a logic probe that shows the logic state:



If the green LED is lit, the input is high; if the red LED is lit, the input is low or disconnected. If they are both lit, the input is constantly changing states.

If you wanted to improve on it, you could use a 40106 which is a hex Schmitt-trigger inverting buffer. You could also use a 4093 quad Schmitt-trigger NAND, and just tie each two inputs together to change them into inverters.

As shown, R2 is selected for operation at 5v. If you wish to use it at up to 15v, you will need to increase the value of R2.
 

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bertus

Joined Apr 5, 2008
22,264
Hello,

My probe can be converted to Cmos.
Keep in mind that Cmos has a lower current output for the leds.
Perhaps add some buffers for the leds.

Greetings,
Bertus
 

Wendy

Joined Mar 24, 2008
23,396
I was figuring on CMOS on the front end, the existing schematic on the back. Basically matching logic to logic.
 

Thread Starter

bundick

Joined Dec 19, 2007
97
I aplogize for not getting back. I didn't get any notifications of reply's.
Too late in the day to think now.
Dick
 

Thread Starter

bundick

Joined Dec 19, 2007
97
OK, looking at both the probes, it seems like that's a Digital sensing device.
What if I'm looking at a wide range of AC, such as a Sound amp?
Or the output of a Coil or transformer coil that is sensing a Rotating magnet?
Will those spikes kill the Cmos Logic probe?
 

SgtWookie

Joined Jul 17, 2007
22,230
OK, looking at both the probes, it seems like that's a Digital sensing device.
They are.
What if I'm looking at a wide range of AC, such as a Sound amp?
Or the output of a Coil or transformer coil that is sensing a Rotating magnet?
Will those spikes kill the Cmos Logic probe?
Most likely, yes.
Neither TTL nor CMOS IC's should be subjected to voltages outside of their "rails", or they may be destroyed.

TTL uses power rails of ground and Vcc (+5v); the +5v can range from 4.5v to 5.5v
CMOS uses power rails of Vss (ground) and Vdd; Vdd's normal range is between 3v and 16v. Some 4000-series CMOS IC's will go up to 18v.
 

Thread Starter

bundick

Joined Dec 19, 2007
97
thanks,
So for my monkeying around with small generators I should use Bills probe with a current limiter in the input of a 222 Transistor, a 12V supply with a current limiter, and a parallel circuit to protect the LED.....
The next step is to make a probe with two LED's. A positive LED and a second LED to show a negative going pulse. Below Zero Volts.

I am thinking of making a trickle charger on a small engine. I have a large chunk of Ferrite with three legs, and some wire wrapped around its legs.

I think the Flywheel has a large magnet oriented +- going by, then followed by a smaller magnet oriented -+.
I think I'm going to get three large rises followed by three smaller negative going spikes.

A volt meter is too slow for this stuff. (I have both kinds)

When I saw Bill's schematic I thought this might be just the thing. Thanks for your inputs. I see its going to be some thing else now.
 

SgtWookie

Joined Jul 17, 2007
22,230
Gee, why not just get an alternator out of a junked compact car, hook it up to the gas engine with a V-belt and wire that in?
 

Thread Starter

bundick

Joined Dec 19, 2007
97
Sarge I went over that last two months. It's just not feasible.
Back in the 50's I worked on some motor cycles (Brit's) that had a small Generator up front for Six volts. It had to run faster than the engine.
To do the same with a Lawn mower engine or small outboard the engine turning 3600, the Alt would be turning 7000 to get what the out put needs to be in order to operate a starter. Only a Briggs 5 hp and above has the torque and sturdy oiling system to do that.

My idea is to make a trickle charger that would charge a Capacitor to operate a pair of small solenoids. The whacko inventor at work here :)
 
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