Go Down

Topic: 555 timer not resetting when connected to two relays... (Read 10727 times) previous topic - next topic

MAS3

#30
Jan 12, 2014, 06:58 pm Last Edit: Jan 12, 2014, 07:01 pm by MAS3 Reason: 1
The 555 charges a capacitor.
If it is at a certain level, the output is changed and the capacitor is discharged,

Your relays may draw too much current and cause the circuit to oscillate (which it was designed to do anyway, but at a different frequency).
That would be caused by an instable power to the entire circuit, triggered b y the relay current.
This oscillation is probably what you hear as the buzzing noise.
A diode can be compared to a transistor.
Why don't you try to use a transistor to switch the relays and see what that does for you?

A H bridge consists of transistors, but it can not be  built with just a single transistor.
Have a look at "blink without delay".
Did you connect the grounds ?
Je kunt hier ook in het Nederlands terecht: http://arduino.cc/forum/index.php/board,77.0.html

twang

I think I finally get it now!
I will add a transistor and I will post about the results


Why don't you try to use a transistor to switch the relays and see what that does for you?

A H bridge consists of transistors, but it can not be  built with just a single transistor.



I did not understand when it was mentioned to use transistors; I thought that I was being told to replace the relays with a 4 transistor h-bridge. I built this h-bridge before and I didn't like it. It drew too much current.

So this is what I plan to do with the transistor, the picture polymorph showed:


I'm not that transistor savvy :smiley-sweat: ; I'm planning on using a 2n2222 with a 1k resistor before the base?
The last time I used the 2n2222 with 9v I ended up using the TIP 31 instead...

MAS3

That should do.

Maybe it would be a good idea to play a bit more with transistors, because understanding those will be of great help to you in future projects.
Have a look at "blink without delay".
Did you connect the grounds ?
Je kunt hier ook in het Nederlands terecht: http://arduino.cc/forum/index.php/board,77.0.html

twang

Yea thanks a lot MAS3,

I've played with the 2n2222 before, but one project got me extremely confused.
I understand that by applying current to base (a small current; a signal) it will connect collector to emitter.
One project I applied small current to base and small current went through the collector to emitter; only when I had the same current did it flow properly.

The TIP 31 worked the way I expected it to.

I guess I will start playing with transistors more and try to learn the math.
wow, V=IR is still something hard for me to comprehend.

I will add a transistor soon and follow up with the results.

polymorph

You keep saying "but it is working", but it is not or you wouldn't be here. Since you won't believe any of us about connecting pin 4 to Vcc:

http://www.555-timer-circuits.com/common-mistakes.html

Quote
3. The reset pin (pin 4) is internally tied HIGH via approx 100k but it should not be left floating as stray pulses may reset the chip.


I cannot find any information on a KE17555 timer. I am familiar with the 7555 from a variety of manufacturers, they are CMOS 555 timers and don't do well with big loads on pin 3.
Steve Greenfield AE7HD
Drawing Schematics: tinyurl.com/23mo9pf - tinyurl.com/o97ysyx - https://tinyurl.com/Technote8
Multitasking: forum.arduino.cc/index.php?topic=223286.0
gammon.com.au/blink - gammon.com.au/serial - gammon.com.au/interrupts

twang

Thanks, polymorph,

I was misunderstanding the "current issue" the whole time it was mentioned  :smiley-sweat:
I'll tie pin 4 to Vcc and I will add a transistor... as soon as I can get my hands on this circuit again.


twang

Hey it works!

Thank you everyone for helping me out with this.

You can see what I was doing here:
http://www.instructables.com/id/Another-Chemical-Agitator/
http://tsjwang.blogspot.com/2014/01/pcb-agitator.html

I really want to thank you all for helping. If you have a dogecoin address you can reply with it.

Thanks, it is solved.

Go Up