555 timer output amp

[dahrich]

Hello:
I want to add a transistor or CMOS amp to the output of a 555 timer.
Can anyone direct me to a circuit diagram that shows how to do this.
My requirement is to drive a .75- 1 amp load.
The diagram needs to show the part number and/or component valus.

Thanks in advance.
Richard

 

[ericgibbs]

hi,
What voltage is powering the 555.
Also what is the voltage supply for the 1Amp load.?

It is possible to add a transistor or MOSFET to the output of the 555 to drive a high current load.

 

[dahrich]

Hi:
What I want to do is drive a small dc motor with a 6 v battery.
My VOM shoots past 150ma when the motor is turned on.
Since the 555 is speced at 200ma I'm concerned about burning it up so I wanted a pretty good factor of safety by connecting the 555 to a transistor or CMOS for more power.
I probably don't need 1 amp capability but I think I should have at least 600ma

Richard

 

[Reloadron]

Hi Richard

I would likely think about using a Logic Level N Channel MOSFET similar to this one configured in a circuit like the attached. That would likely work out. You may want to add a 10 K resistor between the MOSFET gate and ground to make sure it turns off when it should be.

For an amp the MOSFET is somewhat overkill but it would work.

Ron

 

[dahrich]

Hi Ron:
Your solution is exactly what I needed.
Thank you very much.
I thought it would be this simple but exactly how to connect the parts and what parts were needed was what I didn't know.
Regards,
Richard

 

[dahrich]

HI Ron:
You helped me before so I thought I'd ask another question.
Do you know if a 4017 counter's outputs can be used to trigger or reset a 555 timer?
regards,
Richard

 

[Reloadron]

Without looking the trigger in and reset in of the 555 are a logic low. The 4017 when counting sequentially makes outputs high. It can be done but you would need an inverting buffer shoved in the picture. Maybe something like a 4049 hex inverting buffer and using two of the six in the 4049 package. That or maybe a few NPN transistors like 2N2222 or 2N3904 so when the base is high they place a low on the 555 reset or trigger.

Ron

 

[dahrich]

Hi ron:
Thanks for the quick reply>
I understand what you just said. One more question: Can one of the 4017 outputs be used to reset one 555 and trigger another 555?
In other words can one 4017 output be used as input to multiple IC's?
Richard

 

[Reloadron]

If we look at the data sheet for the 4017 Decade Counter/Divider we see it is a low power device. I would use an inverting buffer or transistor as I mentioned. When we look at a chip and want to drive something with it we look at what is called a fan out and we look at how much current the chip we have can source of sink. Then we look at what we need. Consider if you plan to have a 4017 drive a 555 reset and trigger functions you will need to invert the signal anyway.

Ron

 

[dahrich]

Ron:
Looking at the 4017 data sheet it say it can drive two 74L or one 74 LS IC.
So if I understand I should be able to connect the 4017 output to the 74L and then the 74L output to the 555. Is this a correct understanding?
Thanks
Richard

 

[Reloadron]

Not quite but close. Basic 74 series chips like 74LS or 74L are strictly 5 volt chips. Later came the CMOS versions like the 74HC series that use CMOS voltages. I am not sure what your circuit voltages are and thus for an inverting buffer suggested the chip I did.

Ron

 

[dahrich]

Ok I can use a 2N3904 but do you think I can connect two 3904's to one 4017 output?
I really appreciate your patience with me on this.
I understand in general the circuit design but the specifics of the diffenent devices and what's important when connecting them is not something I learned.

 

[dahrich]

Ron:
I got your reply and posted this reply but for some reason when I log on your reply and mine do not appear so I am reposting.
Ok I can use a 2N3904 but do you think I can connect two 3904's to one 4017 output?
I really appreciate your patience with me on this.
I understand in general the circuit design but the specifics of the diffenent devices and what's important when connecting them is not something I learned.
BTW: I just noticed you're from Cleveland. I was born and raised in Cleveland and went to Case. Where abouts in Cleveland are you?
Richard

 

[Reloadron]

Hi Richaard

Yep, here in the Cleve I sit, a displaced New Yorker. We live in Bedford Heights in the SE burbs. Long story how I ended up here but it has been home for a long time. In a few years I'll retire and we are going south. Case is a great school.

Really if you are going to only work off a single 4017 output you only need a single transistor. A single 2N3904 will deliver I believe a few hundred mA and the 2N2222 up to about 800 mA. Attached is an example. The base resistor will be a function of the voltage used.

What exactly are you doing?

Ron

 

[dahrich]

Hi Ron:
I'm retired and have been for 14 years.
We moved from Cleveland in 1966 to Connecticut and from there to California in 1969.
Been in CA ever since and San Diego for the last 6 years. My work experience was in computer controlled automatic machinery and engineering management in the later years. I always enjoyed what I did but have not regretted for a minute retiring. Too much to do and not enough time.

I'm making a diorama and what I want to do is start a motor with the 555 and have it rotate for a certain number of counts. When the desired count is reached I want to shutoff that motor and have another 555 immediately start another motor.

Richard

 

[Reloadron]

Hi Richard, and understand. My CA years were around 75 through 81 with 3 years in San Diego and about 3 years in Anaheim. After the military I worked DoD for a number of years. I enjoyed CA and the climate. San Diego I really enjoyed.

Ron

 

[dahrich]

Hi Ron:
We too like San Diego. We we in the Los Angeles area when we first arrived, then to Santa Barbara for twenty years and now San Diego. We are enjoying SD becasue there is so much to do here: Symphony, the Padres, Chargers, various venues for entertainment, the harbor, and of course you can't beat the weather. On Friday's my wife fixes breakfast, we take our chairs and go to the beach to eat. Been doing this for years.

The Del Mar race track has a hat contest every year on opening day. It's the place to be and great fun to go and see all the ladies dressed in their finery and hats. So, it's things like this that make SD so enjoyable

With respect to my question about driving two transistors from one counter output: is it OK to do this?

Richard

 

[Reloadron]

Yes, you can drive two transistors from a single 4017 output.

Yes, I always did love San Diego, as you said, there was so much to see and do.

Ron

 

[dahrich]

Hi Ron:
Thanks again for all your help.
I just ordered several transistors,timers and counters so the fun will begin.
I have made a circuit using a 555 and soldered everything onto a PC board but this time I also ordered a Breadboard Kit. This job is more complicated and I think it's best to breadboard first.

Richard

 

[Reloadron]

Hi Richard

Always breadboard first.

Keep us up on how things go.

Ron