Transistor astable multivibrator problem

[audioguru]

If I understood right I can use two trimmers instead Ra and Rb and the time device 1 is on will depend on the trimmer 1 and the time device 2 is on will depend on trimmer 2.
Am I right?

yes.
But add a low value resistor in series with each pot to limit the max current.

 

[Letniq]

By "pot" do you mean the trimmers?

 

[BrownOut]

A trimmer is a kind of a pot.

 

[Letniq]

Thanks, dudes I will try the 555 circuit and I will let you know the result.

 

[audioguru]

A pot (potentiometer) is a full size volume control or is larger.
A trimmer pot is a small pot that is adjusted with a small screwdriver.
A trimmer capacitor is a small variable capacitor that is also adjusted with a small screwdriver.

 

[Sceadwian]

It should be noted that trimmer caps have to be adjusted with special plastic screwdrivers which don't have a high dielectric constants and also have low conductivity.

 

[BrownOut]

Thanks, dudes I will try the 555 circuit and I will let you know the result.

Start with about 1Meg trimmers, and 100uF timing capacitor. Leakage in the cap makes it hard to calculate exact values, as the normal equations yields values that are too high. Experiment by adjusting the trimmer till you get the time interval you want.

If you want the same "off" and "on" times, **broken link removed** has a circuit that requires only a single trimmer for time adjustment. See Figure 10 under "Example Circuits" near the bottom of the page.

 

[Hero999]

Yes, if you want a dual LED flasher, I'd recommend building the circuit below.

**broken link removed**

 

[Letniq]

OK I'm finally happy with the result I've get it done with 555N and diod from pin7 to pin6

**broken link removed**

TODO:
-implement optrons and triacs
-make AC motor power regulators (I have no idea how to do it and haven't done research yet so if you now so good and easy to make circuit .. share )

Thanks, guys You helped a lot on this first part of my project

 

[Letniq]

And here is the final
The multivibrator with implemented optrons and triacs

**broken link removed**

 

[Hero999]

Good, I'm glad you got it working.

No offence but it's not very neat and tidy is it?

Putting the little bit of effort into making it look tidy actually increases the chances of it working first time because: you've taken more care building it, better quality soldering will produce more reliable joints and reduce the risk of short circuits, and a neatly designed circuit is easier to fault find. The bottom line is it can actually save time because less time is wasted on diagnosing assembly errors.

 

[Letniq]

It's just a prototype
Know I need to do PCB design and order some PCBs

 

[BrownOut]

It works. That's what counts. Good job

PS: Can you post a schematic? There is another member working on something similar that might benefit.

 

[Letniq]

Here is the scheme. It's not very clear and value of the elements aren't there but the software that I'm working with is not showing them. Where it is written Pompa1 and Pompa2 I mean motor1 and motor2. I hope it is helpfull.

**broken link removed**

 

[Hero999]

The schematic looks sensible to me.

 

[BrownOut]

T1 & T2 appear to be wired backwards to me.

 

[Letniq]

T1 & T2 are working fine. I've already tested the scheme.
There is only one problem that I don't know how to solve.
It's not happening all the time but from time to time. The motors start to vibrate when they should be turned off or there is a peak when the motor starts. I think It is because C3 & C5 should be 50nf but they were out of stock and I get 100nf and this is may be the reason. Can someone help me on this?

 

[BrownOut]

You problem might be related to the way t1 & t1 are wired.

 

[Letniq]

It's BT134-600 triacs.
1-main terminal 1
2-main terminal 2
3-gate

I don't think that it matters how 1 & 2 are connected.

 

[BrownOut]

It does matter. The current for the gate should come from the same as terminal MT2.