Can you post a schematic of what you have and want to do?

Ken

 

This is your circuit I found online, same as the one you posted on this thread.
D was your original output and what I need along with D to drive my second bulb is the last one.
In words, during the flashing period, the 2 bulbs will alternate. After the flashing , both the bulbs will light up together. I need your help on how to make an inverting gate (NOT) using a transistor and wiring both the inverted outputs to the final bulb after adding them (OR).

 

I think this will work.

Ken

 

Thanks Ken, I will test and reply sooon.

 

I did that very quickly...and now I see a problem with it. Don't bother trying it. I'll take another shot at it later.

Ken

 

OK, a little more thinking. It does get more complicated. I think this works...at least in my head.

Ken

 

I tested the ckt you posted before the above one and found a minor problem of Q4 drawing too much of the collector current from Q1, and as a result Bulb 1 stays lit and Bulb 2 blinks as it should. So I added a 100k resistor before D2 and solved the problem.
Now it works good with your previous circuit.

Is there any trouble in following the previous one? I'm happy with it. Thanks a lot Ken. Also I would like to have your permission to publish this ckt on my website.

 

Yes that was the problem,but since I didn't have a way the bench test it after I saw that problem, I opt'ed for the second circuit. Happy It's working for you.

Ken

 

Thought I'd upload the redesigned circuit.

 

Ken, which CAD soft do you use for illustrations??

 

ExpressPCB http://www.expresspcb.com/

It's pretty intuitive and easy to make new schematic or PCB components...and it's free.
The down side is you are locked into their PCB house. But, their "mini board" price is OK for me.
I frequently use the PCB layout program to create a layouts for one-off, point-to-point wired, perf-board projects. The schematic and PCB are linked so you can find layout errors. If components don't have 0.1" (12.5mm) spacing, just create new ones that do.

Ken

 

Hi,

If you modify the oscillator to run in a single gate, you free one for making a complimentary output - like this:

 

Hmm.. seems interesting. Thanks, but I'm planning to settle on the last one as I dont have time now for benchtests. Will try it another time.

 

Soren,

I like the way you freed up the extra gate for me.

JJ,

Sorry I couldn't leave it alone.

Ken

 

Hmm.. This looks better, should I give it a try??

 

I haven't bench tested it, but i think it should work. Give it a shot.

ken

 

Will do a bench this evening as it seems easier to solder on a common PCB with fewer components.

 

I benched it and works good. One problem is that the duty cycle isn't 50%. Around 60-70%. Dont have a scope to measure. Still it works good as a light flasher. Also R5 and R4 values both need to be 100k as the flashing is too quick and the 50k doesnt provide enough room for adjustment and the major variations occur after 100k. I used the components from the previous circuit and now I have 3 resistors and a transistor left over. You guys are great. I think I can now solder this ckt. Or any more mods??

I like the way you designed this circuit. I never thought that an oscilator could be made with an RC and a NAND gate. How do you calculate the frequency? I've been into electronics since a few yrs and I learned a lot but the only one thing I can't manage is transistors. I can't get to design a circuit with transistors as I jump into some sorts of error somewhere. Do you have any idea where to learn about this thing. The only way I learn abt them is when I experiment with them. Rest everything in electronics seems ok and I love to use IC's and design with them. Anyway keep it up guys.

 

Schmitt triggers have hysteresis, that's why the unequal on/off times. I think there is a way to get an ~50% duty cycle with the one Schmitt NAND gate oscillator. I think you have two sets of feedback resistors/pots. A diode is placed in series with each set. the diodes point in opposite directions. The sets are paralleled. That way you can set the charge and discharge times independently.

Component values due vary a lot with the specific circuit. Just use what works.

Ken

 

Hi,

How do you calculate the frequency?

Study the 4093 datasheet - formula is on page 4 and the numbers you need is on pages 2 and 3.

For a quicker (somewhat less precise) approach, you can use:

fq = K/(R*C)

Where:
fq = Frequency in Hz
R = your resistor in Ohm
C = your capacitor in Farad
K = 1.2 (sometimes given as 1.3)


To get a M/S ratio of 1:1, perhaps try another 4093 (preferably from another manufacturer), or adjust the load on its output to get V_tH and V_tL symmetrical around Vdd/2.

You can use one of the six inverters in a 40106 the same way, as long as you don't need to gate the oscillator on/off.