Need to use 74HC14 IC, not 40106B

Thread Starter

doug08

Joined Jan 30, 2011
153
In the circuit below. I already made a voltage divider to supply 6V to pin 14, instead of the 12-13.8V supply. All other 12v connections remain the same as the schematic. I also replaced the 1k resistor from the collector of Q2 with a 2.2K. I left the 680K as is, but thinking I should raise that to 1.2M. Any ideas? It works, but not right because the resistor values are not correct. I do have 6V at pin 14 when the circuit is connected and running. I used a 2n3904 for Q2, a 2n5961 for Q1, and a TIP 120 for Q3

Thanks.

 

mcasale

Joined Jul 18, 2011
210
So, exactly what are you trying to do here? It looks like you are trying to amplify SOMETHING from the pickup and have it turn on a bunch of LEDs.
 

MrChips

Joined Oct 2, 2009
21,074
I presume that this is a timing strobe light.

Why bother use a 7414 or 40106. This is simply two inverter stages with an integrator in between?

I would replace this with two transistors.
 

Thread Starter

doug08

Joined Jan 30, 2011
153
Yes, it is a timing light circuit, and I already made it. So I would like to use the 7414 IC. If you were going to use the 7414 instead, what would YOU do besides adjusting the Vcc to 6v?

Thanks
 

Thread Starter

doug08

Joined Jan 30, 2011
153
All I had was a 74hc14, otherwise I would have used the 40106B. So all I should worry about is just the Vcc? leave everything else as shown in the schematic? Put back the 1K resistor?
 

Thread Starter

doug08

Joined Jan 30, 2011
153
VERY hard to get things where I am located. I "May" have a 4069 ic. That is a drop in replacement? Pinout the same as the 40106B?

Thanks.
 

MrChips

Joined Oct 2, 2009
21,074
The 40106 and 4584 are inverters with Schmitt triggers.
4069 is a plain inverter. In your circuit it should make no difference. Pinouts are the same.
They will all run at 12V.
 

Thread Starter

doug08

Joined Jan 30, 2011
153
I do have 4069's. I will de-solder the 74hc14, and install the 4069, and put back the 1K resistor instead of the 2.2K.

Thanks
 

Thread Starter

doug08

Joined Jan 30, 2011
153
Works, but the light does not show the timing marks. I tried replacing the 680K with a 1M pot. No difference. How do I adjust it?
 

MrChips

Joined Oct 2, 2009
21,074
Are the LEDs bright enough? Can you see the LEDs flash with fairly good intensity.
Are you doing this in bright sunshine or in the shade?
Try doing this in the garage/shade/dark/cloak over your head and engine.
Mark the timing marks with white chalk.
You should see the flywheel stationary (synchronized with the ignition timing).
 

Thread Starter

doug08

Joined Jan 30, 2011
153
Nice bright led strobe. Does not show the timing mark. I made other types before which worked fine. If I add to the 6.8nF cap, it makes the led brighter.
 

Ron H

Joined Apr 14, 2005
7,014
Nice bright led strobe. Does not show the timing mark. I made other types before which worked fine. If I add to the 6.8nF cap, it makes the led brighter.
The 680k and 6.8nF cap are part of a pulse stretcher. Make the time constant (R*C) larger, and the pulse will get wider, i.e., your LEDs will stay on longer. If you make it too long, the timing mark will appear smeared, getting worse as the RPMs increase.

What is the inductive pickup sensing? Are you sure it's mechanically aligned properly?
 
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