Yes and no.Did it work?
Yes, that is what I have ended up with right now, except the 22k resistor you have is the 33k the Mik suggested, and I still have the diode from his suggestion in place. (I have to admit that I'm not sure why the diode is needed, but hey, it works )Søren;60108 said:This will:
It will work with a vide range of resistor values. It should just be large enough to avoid unneded current consumption and small enough to be able to deliver the needed base current for the relay driving transistor.Yes, that is what I have ended up with right now, except the 22k resistor you have is the 33k the Mik suggested, and I still have the diode from his suggestion in place. (I have to admit that I'm not sure why the diode is needed, but hey, it works )
Seems OK.See my hacked up circuit diagram attached. (NOTE: I have no idea what resistor values to use - just went with what was in the original.)
Not that I am going to tinker with it any more as it is now working. Just want to understand how this all works and see if what I think should work makes sense to you gurus.
This should do:I want to try making this circuit even simpler, by using just a 555 and a relay. (No 4020 counter as I really only need the timing to be between a minute to 10 mins max.
The kit instructions said D1 was used to discharge the capacitor C3 when the power was turned off. Frankly I didn't think that would work and didn't think it was all that important to discharge anyway!Søren;60337 said:Not sure which diode that would be, but even the D1 from the original circuit seems to be thrown in for no reason at all - it's not needed.
Yes, I thought so too. If I find I have some free time, I might try it out just to see if my theory is right. I purchased some bread-board the other day, and the ICs in the circuit are in sockets, so I should be able to pull them out and tinker with them easily enough.Søren;60337 said:Seems OK.
Thanks for the circuit and the formula. R3 shows "1..10K". Does that mean it can be any value between 1 to 10K?Søren;60337 said:This should do:
Hi Soeren,Søren;60337 said:Hi,
This should do:
The regular (i.e. non-CMOS) 555, when run from 12V, can handle relays with a coil resistance of 60 Ohm or larger.One question: Can a 555 handle driving a relay directly or should it really drive a transistor that switches the relay on or off? If the latter, can you make a suggestion as to what transistor to use, and any associated current limiting resistors required?
You are welcome and yes, it beats hanging out on street cornersThanks for your help so far! I have it all working on a tidy little piece of bread-board, driving an LED at present. I know, very simple stuff, but I'm happy to be dabbling in electronics again.
Exactly, but I guess you found outR3 shows "1..10K". Does that mean it can be any value between 1 to 10K?
Hi S0ren,Søren;63903 said:The regular (i.e. non-CMOS) 555, when run from 12V, can handle relays with a coil resistance of 60 Ohm or larger.
I haven't ever seen an automotive relay with such a low coil resistance - 150..200 Ohm is quite common for a 40A automotive relay.
|Thread starter||Similar threads||Forum||Replies||Date|
|How to adjust duty cycle of 555-timer circuit?||Digital Design||14|
|555 circuit skin effect?||General Electronics Chat||1|
|Timed circuit to replace a broken boiler timer.||Analog & Mixed-Signal Design||6|
|S||turn on my timer circuit when a DC motor stops running||General Electronics Chat||10|
|B||Simple Timer Circuit||Sensor Design & Implementation||8|
by Ikimi .O
by Jake Hertz