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11 жыл бұрын

555 T-Shirt: www.zazzle.com.au/classic_555_...
Hacking the Mantis Elite microscope to control the LED brightness with a 555 PWM circuit.
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Пікірлер: 367

@JesusisJesus 10 жыл бұрын

Dave should do a video series called 555 things you can make using a 555.

@badgermost 10 жыл бұрын

Oh yeah!

@jonathanpeden9930 9 жыл бұрын

Bless you, what a great idea...

@JesusisJesus 9 жыл бұрын

EEVblog Hear that Dave, Your People want you to do this series. A million views per video at $300 / million = $166,000 in KZfaq revenue. I would only ask for a meagre 25% cut.

@DerStoeppel 7 жыл бұрын

jesus doesnt need money =]

@ufotofu9 6 жыл бұрын

I like that!

@00Skyfox 8 жыл бұрын

I love easy projects like this! They're great for learning the basics of things like timers, dimmers, etc.

@KPPMt1n7 9 жыл бұрын

Dave...you just screwed Mantis out of doing a $300 accessory light dimmer for their microscope.

@applefanXXX 6 жыл бұрын

What he's actually done is give them the blueprints necessary to steal the idea, manufacture and trademark it, and then take legal action against him. #CapitalismBaby

@thekobaz 6 жыл бұрын

And this video will demonstrate prior art!

@boblewis5558 6 жыл бұрын

They could do all that but "prior art" prevails and their action would fail. Besides, whilst the specific (clever) usage is for the Mantis in this instance the basic circuit exists in probably 10 million posts on the web ... do you think Dave really cares?

@lamjeri 4 жыл бұрын

@@boblewis5558 I have seen the second version even on Great Scott's channel. Only difference was that I didn't quite understand the fact that pin 7 is used as an output. 18:50 is quite a jaw dropper for people just learning.

@boblewis5558 4 жыл бұрын

@@lamjeri a quick look at the internal circuit block diagram of a 555 would explain that confusion. BOTH pin 3 AND pin 7 are effectively output pins. Pin 7 being labelled "discharge" doesn't mean it cannot be used as an "output" pin because internally it is basically just an open collector of an NPN transistor, which when switched on provides a discharge path to ground for the timing capacitors. Pin 3 conversely has an output drive circuit which has its own "pull up" internally, hence the lack of need for the external pull up when used as the "discharge" pin. A clever use of basic understanding of the internals to "reuse" the chip in a clever component reduction. An engineering solution to the ever present "bean counters'' desire for cost saving, no matter how trivial! It might surprise people starting to learn, but even engineers with decades of experience can be surprised by novel uses of a circuit because someone has realised the "detail" and how it can be used alternatively. A classic example is the use of 3 logic inverter gates to produce an oscillator. Not something that might easily occur to someone just starting out in electronics but very old hat to someone of experience.

@danaleslie 11 жыл бұрын

Good to hear you're still working on it. One of my favorite EEVblog segments!

@Kezat 11 жыл бұрын

Thanks Dave for this fun little video. It was great seeing you working on stuff in a bit more real time and hands on.

@Nono-hk3is 5 жыл бұрын

Thanks for showing the traditional version of the circuit before optimizing it. That's very helpful.

@grundell2930 5 жыл бұрын

This is one of your best vids Dave

@SarahWattCA 9 жыл бұрын

Cool stuff. My preference would have been to use circuit 1 with an N-channel MOSFET as a low-side switch. Circuit 2 was a clever solution though and I never would have thought of it.

@bernym4047 Жыл бұрын

That would be my preference also. Thanks.

@bernym4047 Жыл бұрын

Dreat educational project and demo of making a PWM circuit from 555. Many thanks.

@3deeguy 5 жыл бұрын

Thank you for posting. I didn't notice until the second day that BOTH sides of the potentiometer were connected to power through a 1K resistor.

@drobinson2299 9 жыл бұрын

I had subtitles on for a few of these videos, as I didn't have my headset around. The way you're voice is automatically made into subtitles had me cracking up give it a try some time, just turn captions on when watching a video back. I wanted to do something exactly like this myself, I'm going to copy the final circuit and wire it up to my own mantis. Amazing they did not include something like this for such an expensive price of equipment!

@NGinuity 9 жыл бұрын

Thanks Dave, I've seen a lot of your stuff and keep finding ways to implement things from videos you do. I think I am going to use a slightly modified version of this to make a dimmer for the under-cabinet LED strip lighting I'm installing in the kitchen. On a barely related note, I'm going to buy one of those t-shirts for my wife merely so I can comment on how nice the threshold and output pins look when they're cold :-P

@TheExplosiveSheep 11 жыл бұрын

Definitely the video I have enjoyed the most from you this month.

@jaypae7002 9 жыл бұрын

Informative, clearly explained, outstanding as usual. I have 555 ckts I still use that I made about 15 years ago. I'm now encourage to dust off my scope, meters, etc and build the LED dimmer, which I need... .

@EEVblog 11 жыл бұрын

Yeah, it was basically real time. It's a video I could have shortened a lot in editing, but I figured there was more value in the real-time stuff.

@georgemarkuly8180 2 жыл бұрын

Very good. I like coming of pin 7 . Used that pin in a simple 555 time base circuit on a very simple scope and a 0.1 out from the transistor. .

@QuadfishTym 11 жыл бұрын

Love how elegant and small the final solution is. Considering doing something similar with a logarithmic pot to get a variable boost converter.

@WhitentonMike 11 жыл бұрын

I like the idea of having each side's LEDs adjustable in brightness so you can get some control of the direction the lighting is coming from. An XY pot would be friggin sweet. Run the stick along the diagonal for equal overall brightness and off diagonal for fading from one side to the other. User friendly as heck!

@TheExplosiveSheep 11 жыл бұрын

Loving the ChestCAD Dave!

@Mrsrtheflyingmum 11 жыл бұрын

Good Vid. Dave. I was using your first Bread Board design and changed it to your second design, as its for a differant use I have differant resistors but thanks the new board works much better.

@Trevs-Shed 11 жыл бұрын

Thanks Dave. I will certainly get down to modding mine. And yes, different types of LEDs could well be useful. In fact vision engineering can supply different led banks. Not sure how much they cost though.

@mrtriac3024 7 жыл бұрын

Be aware that NE555's output is not rail to rail, especially in logic 1 state. A resistor(let's say 1kΩ) betweeen base-emitter(BD136) would greatly improve transistor's switching time and would reduce collector cut-off current. A maximum limit current resistor(330Ω or more) at discharge pin(7) or at the wiper is a good idea too.

@gkdresden Жыл бұрын

This is not relevant for the CMOS 555 timer versions.

@elboa8 11 жыл бұрын

Thanks Dave, my favorite type of video.

@aerofart 11 жыл бұрын

Nice one, Dave. Would love to see more episodes like this one where you actually MAKE stuff!

@logitech446 11 жыл бұрын

Hi, Dave, great video as usual. You can omit the 220R too, replace the BD136 with a IRF520N. Did this works great.

@DolganoFF 9 жыл бұрын

This T-shirt sould have DaveCAD written under the picture!!!

@scknight 11 жыл бұрын

Super cool project!

@ConjUK 11 жыл бұрын

Great vid and hack Dave, love it.

@jasoneyes01 11 жыл бұрын

Brilliant Dave

@MagiKnightOne 8 жыл бұрын

Nice video Dave!! I applied your circuit as a comparision between Analog PWM vs. Microcontroller PWM. Pretty interesting behaviour using constant voltage source. I can reach 26% as minimum and 96.76% as maximum. I do not why, but, pretty intersting thoug. Thank you.

@CanadianMang 11 жыл бұрын

Dave, I think it would be great if you made more videos that were like tutorials for electronics beginners and/or intermediate. For example, teaching us how an adc works, or maybe beginner embedded electronic design, or maybe even teaching about microcontrollers, what a dc/dc converter is. Stuff like that.You have so much knowledge that you should share with us.

@Hydrogen4Health 11 жыл бұрын

thank you for sharing your knowledge. it really helps a beginner like me.

@EEVblog 11 жыл бұрын

Ground bounce from inductance of the test lead. No ground clip on CH2 (so uses CH1)

@jesperahman738 11 жыл бұрын

I'd like to see the voltage out of that LM317 when you use the dimmer! I suppose it's jumping all over the place.

@rahuljathar4430 3 жыл бұрын

You should connect a 1k resistor between those two diodes opposite to trimmer. I built the circuit on breadboard and it works fine but when i made it on pcb as a prototype, my smd 555 chips worked good for several minutes and then stopped working. I blew 2 chips and then i searched some formulas, and came to know that the capacitor on pin 6 is getting charged through the resistor, diode and potentiometer and discharging through the diode only directly to ground through an inbuilt transistor on pin 6. Due to very low resistance on the discharge path, when the duty cycle is at maximum, the capacitor is discharging in a very short time and a lot of current is flowing through inbuilt transistor which will eventually blow the chip making it unusable. I dont know how long the dip version of chip lasts with this circuit but the smd chip will blow instantly. So add a 1k resistor in the discharge path!!!

@EEVblog 11 жыл бұрын

Yes, I was thinking that, but the wires are paralleled inside the optic head, so you'd have to have a separate pot and circuit inside each LED half. It would be pretty ugly.

@jrrymiller 11 жыл бұрын

Dave, When I do this circuit I connect the pin 4 to pin 5 this eliminates the need for the small cap and makes for an easier PC board layout.

@PIXscotland 9 жыл бұрын

Would be nice if this could have dimmed one or the other side independently so you could get "side-ish" lighting. That's sometimes useful for component recognition and adds a bit more 3D depth to the image.

@Jones12ax7 8 жыл бұрын

+PIXscotland I think it's just a matter of build 2 units and placing one each side. Good luck

@glenmartin2437 5 жыл бұрын

Good video. Thanks for the instruction.

@ArtoPekkanen 8 жыл бұрын

This video was very informative for a beginner like me :) Thank you so very much!!! :)

@gkdresden Жыл бұрын

You can always save this pull-up resistor in 555 timer astable multivibrators by using its output pin to control charging and discharging of the capacitor. You can also save the base resistor by use of a p-channel MOSFET for switching of the LEDs also from the output pin.

@LuckyImExil 11 жыл бұрын

No worries, I'm not red-green colorblind and the light green is pretty similar to the yellow for me, too ^^ That's something that has been bothering me with quite a few scopes I've used in the past.

@edwinedmondson6440 9 жыл бұрын

Excellent Example!!

@SnowyOwlPrepper 7 жыл бұрын

Lovely. Could a bypass switch be used to get that additional 100 lux.

@nyghost9991 10 жыл бұрын

Great video!!!

@photocanonn 11 жыл бұрын

great video!

@DiveSafariNZ 8 жыл бұрын

Thanks Dave, I'll give this a go later.

@zainaabdin 4 жыл бұрын

Super dave....no doubt

@EEVblog 11 жыл бұрын

That's effectively what a dropper resistor does, converts the constant voltage into a known constant current.

@UberAlphaSirus 11 жыл бұрын

What might be good also it to be able to switch one side of leds off so you can get shadows, can be handy some times.

@EEVblog 11 жыл бұрын

Err, it's a 0.1uF bypass cap... And the regulated 9V input (minus the LM317 drop) limits any possible maximum voltage. Nothing to worry about.

@UberAlphaSirus 11 жыл бұрын

KISS, just change the existing lm317 to a voltage reg with the pot and be done. the led's have individual resistors up to the plug packs voltage for there max draw. Unless you wanted to do a 555 tutorial that is ;). Take care Dave, love your vids.

@killer1479 11 жыл бұрын

hi, i enjoy watching your videos,and also some of the circuits you make... would it be possible for you to make a book of circuits and the diagrams and maybe release it for the ipad ^^ ?

@hefonthefjords 11 жыл бұрын

if you want to see some car LEDs in action, watch some of top gear's tests of the newer ferrarris and lamobs. they all have obvious PWM in their LEDs when you see their highspeed cam footage in the road tests. it's pretty interesting to see it show up in slow mo like that.

@WhitentonMike 11 жыл бұрын

I don't quite know enough about the math to explain it here but the values are based on a formula that determines the values for the fewest parts that will give the most complete spread of values. The formula is also used to determine things like what currency values a country should have for the best use of resources and transaction efficiency.

@Pukkeh 2 жыл бұрын

Nice, simple solution. A fancier solution might use a logarithmic pot, since the human perception of brightness is more or less logarithmic.

@jarrinson29 8 жыл бұрын

Very good, but I have one question, because use 2 leds and non-conventional diodes, such as 1N4007 or the like, or failing that the typical 1N4148?

@bloomtom 11 жыл бұрын

Oh wow, you left LEDs as the steering diodes. This is a lazy hack with a legendary level of purist utility in the design, I love it. "We don't really care, we just want to get this thing working." - Dave Jones

@TheBadFred 11 жыл бұрын

PWM doesn't change the voltage/amplitude like a voltagedivider/pot, it changes the fequency - is like switching on and of very fast. The brightnes is determined if "the switch" is longer on or off (longer on -> brighter and longer off -> less brighter)

@h0lx 9 жыл бұрын

The light mater enclosure seems quite common, I have a thermocouple thermometer in one of these

@mrkv4k 10 жыл бұрын

lol. I didn't even noticed they are supposed to have different colors (same problem as David)... Anyway, I don't think it matters that much :D Good job with 555. It's one of few circuits that survived huge period of time without any major changes, still great..

@metalmolisher666 11 жыл бұрын

And i tryed to explain that i missunderstood that. You are right. It should be well within the kHz range.

@Saurocksall 11 жыл бұрын

u have given me many ideas..... Thanks...

@dalenassar9152 4 жыл бұрын

Looking at "The Big Test" starting at 24:58 I can't see why you would want to dim the LED's at all!!

@dalenassar9152 4 жыл бұрын

Hey Dave!!! I have been looking for a good push-pull 555-based circuit for a LONG time! On your DaveCad drawing, would I get this if I connect a load to your BD136 output (to source current) and pin 3 (to sink current)? a couple hundred mA at 40kHz to 50kHz should be sufficient.

@adamlumpkins2000 11 жыл бұрын

good one dave!!! Do more hacks!!!!!!!

@onurolce 11 жыл бұрын

I agree with you %100. Also I wish to Dave starts to teach about Microcontroller programming such as open source Arduino...

@CoolDudeClem 11 жыл бұрын

Good old 555! So versitile, I wonder if it could be used in a switch-mode power supply?

@circuitsandshortcuts 4 жыл бұрын

Skip the 1K resistor, and swap pins 3 and 7 on the 555. Use pin 7 as the output (it's open-collector) and pin 3 (push-pull) to drive the steering diodes to the sides of the pot.

@WayneJohnsonZastil 11 жыл бұрын

Very nice use of 555 and nice hack. Should should contact them and donate the schematic so they than add it to next version or maybe charge or get free one.

@trafrellik7350 10 жыл бұрын

The video explains it. The P.S. drives a constant current device, so more resistance would simply increase the voltage (across the pot) and deliver the same current to the LED's. A PWM is the perfect answer to this situation, although a non-inverted output would have allowed a higher PWM cycle (10% - 99.9% is better than 0% - 90% for LED control).

@KB1UIF 11 жыл бұрын

Nice and simple , like it !!!

@GogogoFolowMe 9 жыл бұрын

Hi Dave, just a quick question : I don't understand why the frequency is changing in the circuit #2. In fact, when you adjust the pot in one direction, it lower the resistance to load the condensator and higher the res. to discharge it. And vice versa. The freq. must stay the same, why not ?

@AntonioDellaRovere 11 жыл бұрын

Your device has a pretty old National Semiconductor Logo :-) Well, anyway they are part of TI now... Nice Blog Dave!

@TheOriginalEviltech 11 жыл бұрын

Yep, I guess 0.1uF is nothing to be worried about, still i filter most of the PWMs before i feed them in to LEDs or DC motors simply because additional high frequency in a DC motor is 1- more noise and 2- bad for non-dipped coils. I know it's overdoing it, but i think for me it is worth it. I also have slight light induced headaches when the light is too bright or there is some kind of flicker.

@hefonthefjords 11 жыл бұрын

i was in a shop the other day and they had christmas lights up that were obviously PWM'd way too slow compared to the other sets around them. the frequency of the flashes was making me really uncomfortable but my dad who was with me at the time couldnt notice the difference. i guess some people are able to pick up higher frequencies than others.

@palashnathdas2119 5 жыл бұрын

You can replace the PNP transistor with a N channel MOSFET and the 0.1uF capacitor with 47nF capacitor .

@DavidSalter2012 11 жыл бұрын

Great video as usual Dave, but as a red-green colorblind viewer I thought you should know I can barely tell the difference between the green and the yellow on the oscilloscope. Any other color combination would be fine.

@mccelf 11 жыл бұрын

Great stuff, shame I'd already breadboarded a 555 PWM circuit like this earlier today before the video was uploaded. It would've been useful.

@johnkerley4152 10 жыл бұрын

I thought I saw the frequency swing swap when the 555 circuit had the last modification. It was at first lower frequency at higher duty cycle and then it went to higher frequency at higher duty cycle.

@GaRbAllZ 11 жыл бұрын

Great little hack Dave; you are going to have to name it something like the Mantis "DUD" (Down-Under-Dimmer;)

@God-CDXX 8 жыл бұрын

this circuit is a great one for hi load like 2 + amps I tried it on a small motor t I used a IRFP250N for the opt I had a 1 k pull up resistor on the transistor you can hear the switching sounds like a cordless drill 7 amps no heat

@ianide2480 8 жыл бұрын

Having to use what I have on hand, I used an IRL3803 (140 amp rating is a tad overkill) instead of BD136. Between pin 3 and the gate I used 47k and since I have a CMOS version of the 555 as well the cap from pin 5 really isn't needed. I read it somewhere on Talking Electronics that pin 5 need not be connected in CMOS versions for PWM control, or perhaps I misread something, but it works well without the cap... The voltage going to pins 4, 7, and 8 get an additional 220ohm resistor but the voltage going to the FET remains unchanged. I got VERY close to 0-100% according to my crappy sound card oscilloscope.

@basemgamal622 7 жыл бұрын

can this PWM handle high amp's or i have to replace some parts ? EEVblog

@-Graham 10 жыл бұрын

Hi Dave (and everyone!) This is rather inspired, I have seen this circuit a few times (including hackaday) and now i know where it came from. Would it be a simple mod to invert the output so we get ~10% min to 100% brightness? Thanks!

@EEVblog 11 жыл бұрын

Yep, same thing. So called because it "drops" voltage.

@hefonthefjords 11 жыл бұрын

question dave; what is the lux output of the two LEDs in the 555 circuit? how much of the missing 2% of the total lux output of the circuit do they make up? if you were to integrate the whole circuit into the mantis and make those LEDs white could that help make the whole thing more efficient in terms of lost original output?

@mrkv4k 10 жыл бұрын

It could be done with pot and one transistor as a current source (pot in emitor, base at dc bias). The current source with lower current would "overide" the other one. Anyway, this is much nicer solution.

@EEVblog 11 жыл бұрын

Every scope is that "sensitive". Welcome to the wonderful world of probing!

@johnkerley4152 10 жыл бұрын

I was wondering, what do you think about the use of such a circuit to make an LED put out more light by pulsing higher than normal forward current at a low duty cycle and high frequency?

@TheBadFred 11 жыл бұрын

That's the hacker's spirit I wanted to ignite with my proposal of the PWM device in between the Mantis and the power supply.

@insylem 7 жыл бұрын

Also, since it was only 1/2 amp current, why not just put the pot on the 317 and make it vairy the current linerally?

@circuitization 11 жыл бұрын

you can also use this circuit for controlling motor speed...

@robertselectronichobbies9507 6 жыл бұрын

Nice simple circuit but when ever you drive a PNP this way it may not shut off because the base voltage is always a little lower than the supply. A 20K from base to emitter will ensure it shuts off reliably and will reduce power dissipation in the transistor.

@hefonthefjords 11 жыл бұрын

i was referring to frequencies of "flashes" due to the PWM signal, not colour frequency of light. for example, there are times where i have been in office buildings and been able to "see" the flashes of the flourescent lights overhead. obviously its fast as hell but sometimes it's perceptible to me.

@jimmymifsud1 11 жыл бұрын

You've given Dave CAD a new update!

@metalmolisher666 11 жыл бұрын

Add i was giving 2 examples a) frequency of light b) frequenzy of flashing where somebody can be abnormalyl good at detecting light. I see those light flashes in neon tubes too. I just say that there are limits. And that tim was right - pwm sould be in the kiloherz range so you cannot see it.,

@MariaEngstrom 11 жыл бұрын

The thing that amazes me the most is that the manufacturer of the microscope did not include the dimmer function. Would not have affected the manufacturing price by to many fractions of Dollars I imagine. It could even have been used as a selling point. Love the solution. :)

@caddyguy5369 Жыл бұрын

Any ideas to use a 0 to 5v potentiometer to dim RGB without messing up the color mix? I am expirimenting with a PWM fan controller for testing, but if I'm thinking right for the final install I may be able to use the Pam signal from the factory computer that is controlled by the dimmer knob.