1hz, brief pulse from LMC555CMM

Discussion in 'The Projects Forum' started by BlackOps, May 24, 2016.

  1. BlackOps

    Thread Starter Member

    May 23, 2016
    32
    0
    image.jpg
    Hello, i need help with my circuit. Yesterday, i searched the whole entire internet to find something close to 1hz and a pulse duration between 10 and 200 ms. I found some video's, unfortunately they didn't show me any diagrams.

    Question 1: , i'm using a LMC555CMM timer which is an ultra small micro controller, the reason is because it needs to be small. So can i use SMD (surface mount components) directly on the pins to set it up? Like smd resistors and smd ceramic capacitors.

    Question 2: what resistor, and capacitor do i need for 1Hz and 80 ms? I want to use surface mount components.

    Question 3: what is the smallest 555 timer on the market? I heard something of dsbga8 but can't find anything.

    Any information would be appreciated :D

    By the way, if I'm doing something wrong, tell me so I wouldn't do it or i will change it as I'm completely new to this forum.

    Thanks!

    image.jpg
     
  2. dl324

    Distinguished Member

    Mar 30, 2015
    3,250
    626
    Welcome to AAC!

    You can modify this circuit from the National Semiconductor LM555 datasheet to give the desired duty cycle:
    upload_2016-5-24_9-11-7.png

    upload_2016-5-24_9-10-27.png
     
    BlackOps likes this.
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,804
    1,105
    Do you mean a pulse of width in the range 10ms to 200ms and a repetition period of 1Hz?
    If so, this should do it:
    1Hz-prf.PNG
     
    BlackOps likes this.
  4. BlackOps

    Thread Starter Member

    May 23, 2016
    32
    0
    Thanks! I got one more question, actually 2. Can i use surface mount components (components used for small computers like phones, hard drives) for this ic?

    Like a SMD ceramic capacitor and SMD resistors?

    And i see this circuit diagram is for the LM555, can i use the same circuit for the LMC555CMM (the smaller variant) thanks :D
     
  5. BlackOps

    Thread Starter Member

    May 23, 2016
    32
    0
    Thanks for your reply, can this circuit also be applied for the LMC555CMM timer? And can i use SMD components for this like a ceramic SMD capacitor and an SMS resistor? Thanks :D
     
  6. crutschow

    Expert

    Mar 14, 2008
    13,033
    3,241
    Yes and yes.
     
    BlackOps likes this.
  7. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,699
    907
    BlackOps likes this.
  8. BlackOps

    Thread Starter Member

    May 23, 2016
    32
    0
    Awesome, i will buy some 10 pieces of each component including the timer as i love decapping the IC, so i want to see whats inside the timer, and ofcoure, if i somehow manage to get magic smoke instead of the working circuit.

    Thanks for your answer :D
     
  9. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,699
    907
    BlackOps likes this.
  10. BlackOps

    Thread Starter Member

    May 23, 2016
    32
    0
    Thanks for your answer. I will keep an eye on this component, but for now i think i have to do it with an 555 as the gps breakout board is too big and requires more then 3 volts to operate. This is where the circuit has to go in, its a prototype lazer flashlight build. The reason why i use the 555 is, thhere is an BMS inside my designed circuit, it turns the laser of when the battery is drained to 2.20v, but whenever Pin 4 (Vcc) and pin 5 (DP test pin for latency measurment) are shorted to gether, it will go in to measure mode, so it will turn the laser on, but when the bridge is cut ( by 555) it turns it of if voltage in below 2.20v. But i want this pulse so whenever the laser beam starts to blink, it means you have to charge the battery.

    Here are some pictures, the timer circuit has to fit in the shiny barrel

    Btw, on the circuit i made, on the backside is a spring, right above there is a shock switch, this would be replaced by the micro 555 circuit i'm going to build, its a laser diode driver, and advanced one, and i'm trying to fit this inside my prototype flashlight laser which is in the pictures image.jpg image.jpg image.jpg image.jpg
     
  11. dannyf

    Well-Known Member

    Sep 13, 2015
    1,825
    364
    A relaxation oscillator built around a single gate will do that.

    More flexibility with a mcu - more precise as well.
     
    BlackOps likes this.
  12. BlackOps

    Thread Starter Member

    May 23, 2016
    32
    0
    Thanks for the link, i decap them to view the IC from the inside as i love to see them.
     
  13. BlackOps

    Thread Starter Member

    May 23, 2016
    32
    0
    intresting, are there IC's for that? And can they be made as small as an LMC555CMM? Never heard of an relaxtion oscillator. I will look for it too.
     
  14. dannyf

    Well-Known Member

    Sep 13, 2015
    1,825
    364
    in a space-limited application like yours, you will find that the biggest issue is likely to find a not so leaky and not so bulky capacitor - tantalum capacitors are likely your likely bet here, and likely only some of them will work. MLCC caps don't go as high, so to use them you may have to go with a cmos version -> which tend to have limited current capability -> not able to charge up / discharge as fast.

    A mcu-based solution doesn't have those issues. Plenty of 8-pin mcus to choose from and some SOT23-6 chips as well. No external parts needed to get them going - you do have to learn to program them however.
     
    BlackOps likes this.
  15. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,544
    1,251
    BlackOps likes this.
  16. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,699
    907
    Here is an old Fairchild application not about using inverters for oscillators: http://www.fairchildsemi.com/an/AN/AN-118.pdf Figure 6 shows a single Schmitt trigger oscillator.

    If you want to consider a microprocessor, the PIC10F2xx and 10F3xx (there are several) come in a SOT23-6 package, which is quite small and as dannyf mentioned will give you added capabilities.

    John
     
    BlackOps likes this.
  17. BlackOps

    Thread Starter Member

    May 23, 2016
    32
    0
    No external components and SOT23-6 o_0, i wish i had something like that preprogrammed, but i think i lack experience and equipment to do that, but, for the 555, @Alec_t posted a diagram of the timer setup, Can you help me finding the smallest tantalum capacitor with that value to make that circuit work?
    And since i'm still a complete N00b with 555, is his circuit valid for every 555 IC Like the LMC555CMM? I think i will get it to fit, but the capacitor is now the big issue, as i can easily connect the smd components on the rear and on the side of the chip and prop it in there, but the space is so limited that i can't use big capacitors, i can however use some tantalum capacitors, i can even place 2 to 3 of them on top of the PCB vertically, the barrel is 12mm in diameter,

    By the way, the output current is no problem, as it only has to bridge Vcc with PD of the sot23-6 chip, To bypass it to measure mode and back to normal to make the laser light flashing when the battery voltage is below 2.20v, and the battery management circuit is basically what powers the laser, but the 555 idea adds an extra feature.

    So questions,

    Question 1,
    For the CMOS 555 timer, which i will use because its low powered and MSOP-8 which is smaller, can i use the same values as what @Alec_t posted? As i need what he has For the LMC555CMM, that diagram had a NE555, so does that make difference?

    Question 2,
    Since the LMC555CMM is an CMOS 555, can i use SMD capacitors to make an almost to exact same output as @Alec_t diagrams point out, so 1Hz and pulse width between 10ms and 200ms. That would be awesome as that will definitely fit, and its always nice to have such small thing in your hards with so many components and features.

    Question 3,
    Can you help me finding the right MLCC capacitors for the LMC555CMM to make 1Hz and a pulse width of 10-200ms?

    Thanks for your answer :D
     
  18. dannyf

    Well-Known Member

    Sep 13, 2015
    1,825
    364
    Alec_t's circuit is the right type of circuit -> the 555 there is nothing but a NOT gate so you can replace it with a 74HC1G type device, with a schmitt input.

    If your 555 is a cmos type, you can afford to use high value resistors, with the hope to reduce the capacitor to below 1u, and hopefully in the .2u / .1u range. That likely will mean resistors in over 10Meg. If that's where you end up, you can ignore the the resistor in serial with the diode: your duty cycle will be quite small.

    With resistors value that high, you will have to experiment, and you should be prepared for temperature + humidity induced effect.

    You are in a territory where theory deviates materially from reality.
     
    BlackOps likes this.
  19. BlackOps

    Thread Starter Member

    May 23, 2016
    32
    0
    Thanks for your answer, i got another question, i made a diagram. Is there an ic capable of doing this?

    So what I want is, when i tap the laser slightly agains my leg, it turns on. I already have the circuit for that, but i need a switch. I know i can use mechanical switches but they require a hard shock against my leg, i'm sure the laser can take it, but my leg not haha as that this is SOLID. So

    So all in short, whenever i tap it agains my leg, it needs to bridge pin 1 and pin 2 temporarily (not continuously).

    This is what i want, here is the picture, the SOT23-6 package is the microprocessor on my Battery Management System. The G2JF battery LDO ic is seriously idiot.

    I need something similar to this diagram, so it can bridge pin to pin momentary, and the pak is slight, so I don't hurt my leg. So are there any accelerometer IC's capable of doing this? Btw the output current or voltage of bridgpin 2 may not drop. Thanks :D image.jpg
     
  20. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,699
    907
    The MCU's I mentioned will do that easily. As for something analog, what can you tell us about the accelerometer output or a link to its datasheet? I doubt it is an on/off device, but some are analog output, which would open up the possibility of using a comparator..

    John
     
    BlackOps likes this.
Loading...