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Breaktru Forum  |  eCigarette Forum  |  Modding  |  Topic: 555 timer PWM mod
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Author Topic: 555 timer PWM mod  (Read 36176 times)

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Offline Zanderist

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555 timer PWM mod
« on: February 22, 2015, 02:49:52 PM »
I went for it with this mod, after finding a low power 555 timer (LMC555) I etched and built it up.  The problems it faces is it doesn't give near 99% duty cycle. It also makes a high pitched noise, not sure on how that happens.
I went for the mod just because it seemed the best idea than having to program a bulky chip. I had ordered (sadly wasting money) SMD but that failed didn't have the skills or the correct equipment to be soldering components that were two pin heads long

Benefit to this build is can vary the power to the coil. Can't say what percentage it goes down to but I do notice the difference. If you hook it to high power transmitter you can tap out Morse code with it.

It's vapor production on the low setting is like that of a tank set up on an ego. On the high setting it feels like an RDA on 1.0 ohm build.

The goal was to improve on the existing mosfet build idea, while it does work ( keeping mind that your battery is near a full charge to enjoy the full benefit) it doesn't match vapor production of the plain mosfet box mod

Now for the pictures, the work put into this was rapid. Also Altoids tins aren't the best because they bend to easily and produce ugly drill holes if using the drill incorrectly. The thing you will notice is some of the parts are just freely floating. That is because I had to rewire the whole thing and add components. Had this been foreseen everything would of been etched and placed on a circuit board ( but not the mosfet, only because of easy access in the even of replacing).

Why I had rewire was that I got trolled from schematic I found on the internet saying that pin 7 was the output...unless there is a way to get pin 7 to output I had to move the wire to pin 3. Once the move was complete I had some form of pwm control. Also the LED was supposed to give an idea of the pwm signal but it some how drew to much power and caused the circuit to, I guess in lack of a better word, stall (no activity). I switched the LED to just show if the device was on or off instead.

What I added  was whole driver set up, what seemed to be going on that connecting pin 3 directly to the gate was not having any effect.  This gave rise to the driver circuit. I used a zener diode (cause I had them on hand) to give me a constant 3.3 volts to make sure the calculations didn't move unless of course it dropped below 3.3 volts.

A strange thing happens when you try to run the octocoupler without any resistance of transistor, what happens is I guess that inside the chip the LED is bright and doesn't power off right away. What this does it makes the PWM have no effect and the mod acts like a regular  mosfet box mod.

I don't know what else to add so I'll just answer questions if any.


edit:(IT'S NOT 120 VOLTS IN THE DRAWING ITS SUPPOSED TO BE OHMS)









Here's the mosfet I used to much success in the basic mosfet box mod build
http://www.mouser.com/ds/2/302/PSMN2R7-30PL-353505.pdf
« Last Edit: February 22, 2015, 02:54:39 PM by Zanderist »

Offline CraigHB

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Re: 555 timer PWM mod
« Reply #1 on: February 23, 2015, 01:00:55 AM »
555 timers are actually a pretty good simple way of doing a PWM driven mod.  However, there are limitations in the duty cycle.  If you add a diode on the trigger/discharge circuit you can improve the range.  Take a look at the following about halfway the page you'll see the circuit; http://www.electronics-tutorials.ws/waveforms/555_oscillator.html  I'm having a little trouble reading your schematic, but it looks you've already done that so you should be able to get close to 100% duty cycle, but it's not possible to actually get 100% without some kind of bypass which adds more circuitry.

Offline Zanderist

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Re: 555 timer PWM mod
« Reply #2 on: February 27, 2015, 03:43:42 PM »
Shameless bump.

I've since improved it, but my favorite part about this mod is in this video

https://www.youtube.com/watch?v=9B58pmgQaJo

Offline Visus

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Re: 555 timer PWM mod
« Reply #3 on: February 28, 2015, 05:50:36 PM »
 :beer-toast:

I used the calc you origin is at 98% duty if you change r2 to 10 ohms you can get 99% I do not know how that would affect how you want your mod to perform tho..  :Thinking:

http://www.ohmslawcalculator.com/555-astable-calculator

Offline Zanderist

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Re: 555 timer PWM mod
« Reply #4 on: February 28, 2015, 07:01:43 PM »
:beer-toast:

I used the calc you origin is at 98% duty if you change r2 to 10 ohms you can get 99% I do not know how that would affect how you want your mod to perform tho..  :Thinking:

http://www.ohmslawcalculator.com/555-astable-calculator

I need to update the drawing but to give you a rough idea of the change I made is this...
 
The whole driver circuit is replaced with a single NPN transistor with a 1k resistor on the base and a 1k resistor at the collector, the gate is connected to the collector pin. It works so much better now but a weird thing happens when I use a PNP transistor instead, in that situation it acts like it has a duty cycle of 0-50%.

I've also added an over engineered low voltage indicator circuit, best part about that is, it works!

What I hope to do, if I figure out how to, is use pin 5 to adjust the PWM as the resistance changes at the coil. Problem I see is that it no longer fits in a Altoids tin because I would have to include rail to rail low power op amp to boost the very small voltage drop that would occur between the coil and the mosfet. Then it would need another op amp acting like a comparator  to give it a reference voltage (to determine temp). However as I explore the idea I begin to see why you can't use Kanthal, as research is showing (google searches) kanthal doesn't change that significantly as it heats up.

As an added bonus, another road to take on this project will call for an arduino. I'm not saying use the 40 pin chip but burn a program on an ATTINY chip (8 pin dip) very easy pwm with the potential to even at a low voltage indicator. Sure maybe no nice LCD to show off, but you don't have to deal with very complicated programming and also allows you to build in smaller boxes.


Offline CraigHB

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Re: 555 timer PWM mod
« Reply #5 on: March 01, 2015, 03:54:39 PM »
I used a 8 pin MCU for a simple little non-ecig project the other day, the program is like 20 lines.  They are handy things, great for simple tasks.  You can do things the analog way, but it's almost always easier to do something using an MCU, even for the most basic tasks.

Offline Visus

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Re: 555 timer PWM mod
« Reply #6 on: March 01, 2015, 04:15:24 PM »
Craig  saw your heli project on YT,  sweet you got good control,  impressive if your just starting out hover mode is hella hard..


Ya I would say so,  the programming thats confusing lol   Its not so bad but gotta learn extra more than stuff lol..

It would make this task extra easy tho..

Offline CraigHB

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Re: 555 timer PWM mod
« Reply #7 on: March 01, 2015, 04:29:25 PM »
Hehe, things get around on the internet.  Yeah that was a fun project.  5k rpm head speed rocks on that little heli.  Just started with the collective pitch stuff a couple months ago, it's a very slow process learning how to fly those things, too many things to control at the same time, pitch, roll, yaw, throttle, collective, argh.

In terms of programming, I actually use assembly which is real easy for me, just need to reference the instruction set, nothing to remember on my part.  C is standard, but I forget how to use it shortly after I review it.  There's a also some decent Basic compilers and interpreters you can use.  I used Basic a bit in the early 80's for some stuff and it was super easy to learn and use, don't remember a lick of it now though.

Offline TheModfatherInc

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Re: 555 timer PWM mod
« Reply #8 on: March 19, 2015, 01:56:13 AM »
we have been building a ton of these lately... this is the what were using currently. ALL CREDIT TO MIKE AKA RELAYER 1974 for the diagrams.

we have been having good results and you can use a 100k-200k ohm pot in place of the 10k to get rid of the whine on this version. the PFet is a buffer for the timer output this allows use of ANY standard or CMOS 555 timer so 3-18v  or so input voltage is possible. were building these up to 16.8v without timer failures on this version. in fact i have 7 open source PCBs designed for this exactly up on oshpark if any of you are interested  WARNING THEY ALL REQUIRE 0805 SIZE COMPONENTS personally i find them easy to hand solder but many people do not. if you wanna dip your toe in the PWM pool, my mini PCB cost 80 cents for 3 SHIPPED. i make nothing off these, just giving back because the diagram was so beautifully crafted and given to me, i got tired of deadbugging these circuits on sockets and decided to simplify things for myself and share with the rest of you
https://oshpark.com/profiles/TheModfatherInc
parts lists are in the descriptions and obviously you arent at all tied to the values in the diagram when you build it, you can calculate your own values, etc.
heres a pic of one for a B box populated by hand (excuse that obvious through hole resistor on an 0805 spot someone forgot to order 15k :/ )


i just ordered up a few attiny85 and am gonna tackle one of those next :)

Online Breaktru

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Re: 555 timer PWM mod
« Reply #9 on: March 19, 2015, 07:39:18 AM »
Welcome to the forum ModFather and thank you for sharing

Offline TheModfatherInc

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Re: 555 timer PWM mod
« Reply #10 on: March 19, 2015, 08:35:59 AM »
TY sir, ive been lurking forever and i registered some time ago and couldnt remember what email it was under so i re-registered. you sir, need to join us on facebook in Box Modders and MCU Mods (as if you have the time LOL) im loving these PWM mods im vaping a 3S 18650 at around a .4 and getting 12 hours off the batteries reliably.

EDIT: it occurs to me now you may be there already lol, but if you arent, you should be. i mean, Mike is in charge so you have to deal with his bullshit but other than that its great ahahhahaha :P
« Last Edit: March 19, 2015, 08:39:59 AM by TheModfatherInc »

Offline Visus

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Re: 555 timer PWM mod
« Reply #11 on: March 19, 2015, 04:37:09 PM »
Hey Mod,

Nice boards


I joined box modders about a month ago yall are nutz I get a lol everyday.. :laughing2: 
Definitely an uncensored group..

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