New Old Guy

Discussion in 'General Electronics Chat' started by Switched, Apr 9, 2015.

  1. Switched

    Thread Starter New Member

    Apr 9, 2015
    12
    0
    Hello,

    My name is Switched aka Ron and I just joined the group. I'm a retired machinist and I need a small scale hobby to keep my mind alive so I have decided to experiment with electronics. Flashlight batteries and light bulbs is pretty much the extent of my knowledge so I might ask questions that will make you all look at one another and scratch your heads. I'm not a dumb or stupid man, I'm just ignorant when it comes to matters outside of my field of expertise. Today I need to know whether I should purchase NE555N or NE555P timers for my 12V timer relay project. I did use the site search function and I did not find an answer.

    Thanks,
    Ron
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,007
    3,233
    Welcome to the forum.
    Give us a few more details about how the timer should work and we can better answer your questions.
     
  3. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,289
    1,255
    Welcome.
    We need more Rons. :D
    I think either is ok, but the P is a newer part so probably better.
     
  4. #12

    Expert

    Nov 30, 2010
    16,283
    6,796
    atferrari likes this.
  5. dl324

    Distinguished Member

    Mar 30, 2015
    3,242
    619
    Hi Ron,

    If you're just getting started, make sure you buy through-hole parts. Much easier to breadboard. 555 timers are pretty much the same, though there are some CMOS versions.

    Since you're just starting with electronics, you should know that any MOS devices require protection from static discharge. Most have built-in ESD protection, but don't depend on it. If you're lucky, ESD damage will kill the device outright. If you're unlucky, it will continue to work, but reliability will be compromised.
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    783
    The suffix is usually package type or may refer to something like "standard or low noise" etc - IIRC; a D suffix is usually SMD package.

    The data sheet should explain all.
     
  7. Switched

    Thread Starter New Member

    Apr 9, 2015
    12
    0
    crutschow,

    Monostable or One Shot timer.

    I want to build my own 12V 15A timer relay. I plan to use the 555 timer to control a relay that will switch 15A current.

    Ron
     
  8. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
  9. DNA Robotics

    Member

    Jun 13, 2014
    123
    26
  10. ScottWang

    Moderator

    Aug 23, 2012
    4,854
    767
    How long are you trying to setup?
    The 555 has its time limited, if you need a long time to setup then you will need some other counter IC to play with.
     
  11. Switched

    Thread Starter New Member

    Apr 9, 2015
    12
    0
    Scott,

    1 to 10 seconds held high.

    Ron
     
  12. ScottWang

    Moderator

    Aug 23, 2012
    4,854
    767
    All resistors are using 1/4 watt
    D1 - 1N4007
    VR1 - potentiometer,pot or VR.
    C1 - Electrolytic capacitor, it has ±20% tolerance
    C2 = 0.01 mylar capacitor
    T=1.1(R2+VR1)*C1 = 11 sec
    You can using VR1=100K and C1=100uf/25V or VR1=1MΩ and C1=10uf/25V.
    LED1 = 2V/20mA/3mm
    R4 = 1.2K
    You can using LED1 = 2V/10mA/3mm, R4=1.2K or LED1 = 3V/20mA/5mm, R4 = 560Ω.
    If the relay turn on, but it can't keep stable then you can reducing the R3 from 10K to 8.2K.
    Sw1 - push button switch.
    Relay - 12V, Com = common pin, N.O = Normal Open, N.C = Normal Close
    Normally we using Com and N.O two pins to control the device.

    555Mono_MonoSwitched_ron_ScottWang.gif
     
  13. Switched

    Thread Starter New Member

    Apr 9, 2015
    12
    0
    Scott,

    I have negative logic. Do I have to invert the signal?

    My application will never vary in the timing between the signals so I will most likely go with a fixed resistance and capacitance. According to my calculations 1.1 * 20,000 Ohms * .000050 Farads will give me a 1.1 second duration. Can you tell me where the constant is derived from? Please excuse my ignorant questions. I'm way behind the class but, I truly want to learn. I'm driven by a challenge but, I cannot drive in the dark.

    Ron
     
  14. ScottWang

    Moderator

    Aug 23, 2012
    4,854
    767
    The constant was came from the manufacturer, you can check in the page 5.
    Let's make clear on the same track, please explain more clearly about your negative logic.
     
  15. Switched

    Thread Starter New Member

    Apr 9, 2015
    12
    0
    Scott,

    My signal closes to ground thereby making it negative polarity. Many parts of my CNC milling machine control also uses negative logic.

    Ron
     
  16. ScottWang

    Moderator

    Aug 23, 2012
    4,854
    767
    I'm not sure that you really understand the meaning of negative logic or not, as the circuit that I attached, the input just need two contacts whatever using the switch or contact of relay.

    Maybe you should describe what are the voltage of your logic level, and label them as 0V, 5V, 12V, -5V, -12V, etc ...
     
  17. ScottWang

    Moderator

    Aug 23, 2012
    4,854
    767
    I added a stage of bjt inverter for the new design.

    555Mono_MonoSwitched_ron_ScottWang-02.png
     
  18. Switched

    Thread Starter New Member

    Apr 9, 2015
    12
    0
    Scott,

    Funny that you would say that because I came to the same conclusion. You must remember that I'm ignorant when it comes to electronics but, I intend to overcome that to the extent that I can before I go into the box. It is hard to bring any homework to class when you are 60+ years behind the rest of the class.

    In forums where I'm the expert it annoys the heck out of me when people make no effort before asking for help. When that occurs then I see it as asking for the complete solution so as to avoid doing any research on their own. To often I do not recall how confusing it was when I was trying to become the smartest one in my fields of expertise. When you have full knowledge then it can appear that those that have little to zero knowledge are dumb as a brick. Sadly most are. I will at least do my own research and if I lack the knowledge to know that it will work then I will submit it for confirmation.

    Assuming that I have to convert the ground signal to positive then will this circuit accomplish that?

    Ron
    [​IMG]
     
  19. #12

    Expert

    Nov 30, 2010
    16,283
    6,796
    Yeabut the drawing in post #12 is a, "Ground to start the timer" circuit. The monostable naturally uses a ground for a trigger. I think you are chasing the wild goose.
     
  20. ScottWang

    Moderator

    Aug 23, 2012
    4,854
    767
    The monostable multivibrator needs a switch to give the input a high to low signal, there are two contacts, but in your pnp circuit, if the input connected to ground then where is the place it should connect to?
    Does the output connecting to the pin 2 of ne555?
    If the situation just like above then this is not what you said as a negative logic, it just a inverter circuit has a low level input and high level output, they are complete different, that's why I want to make sure that you really know the negative logic.

    If your circuit just a inverter then it was also in my plan, but i didn't post it, because I'm not sure what do you really want.

    The Rbe in your circuit is too less almost can be ignore.

    In my circuit already provided a high to low trigger, and in your circuit is also the same then why you want to add that?
     
Loading...