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Hacking the Mantis Elite microscope to control the LED brightness with a 555 PWM circuit.
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[@KPPMt1n7]

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

[@applefanXXX]

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]

And this video will demonstrate prior art!

[@boblewis5558]

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]

@@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]

@@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.

[@JesusisJesus]

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

[@badgermost]

Oh yeah!

[@jonathanpeden9930]

Bless you, what a great idea...

[@JesusisJesus]

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

[@DerStoeppel]

jesus doesnt need money =]

[@ufotofu9]

I like that!

[@00Skyfox]

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

[@SarahWattCA]

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]

That would be my preference also. Thanks.

[@DolganoFF]

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

[@mrtriac3024]

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]

This is not relevant for the CMOS 555 timer versions.

[@NGinuity]

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

[@jesperahman738]

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.

[@PIXscotland]

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]

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

[@rahuljathar4430]

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!!!

[@SnowyOwlPrepper]

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

[@EEVblog]

Sorry, I don't pick the colour.

[@octavmandru9219]

I am curious why not use a npn? did I miss something?

[@VerstehenSieMathis]

Pin 7 can only be "low" or "open", but not "high". In this PNP configuration (#2), when 7 is low, he gets emitter-base-current and therefore current through the LED to ground. With an NPN, he would've had to put current _into_ the base, so he would've had to use pin 3 (which can go high) to put a positive voltage to the base resistor. (And also switch between LED and GND.)

[@EEVblog]

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.

[@drobinson2299]

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!

[@EEVblog]

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.

[@EEVblog]

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.

[@EEVblog]

If I know something has already been done to death, or I have nothing really interesting to add, then I generally am not too interested in doing it.

[@EEVblog]

The diodes instead of LED's would not have improved it in any way.

[@EEVblog]

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

[@EEVblog]

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

[@EEVblog]

That requires people to take apart their mantis. So I wanted an inline solution.

[@EEVblog]

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

[@WhitentonMike]

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!

[@law-ofohms7815]

wouldn't a pot on the LM317 in current control mode be much simpler?

[@tohopes]

he said that he wanted to avoid installing anything inside the microscope case

[@dalenassar9152]

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

[@EEVblog]

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

[@EEVblog]

I need to re-spin the board for a different form factor.

[@unclerojelio6320]

Could you go over again what the two diodes are doing?

[@johnconrad5487]

+Roger Banks rerun the video!

[@boblewis5558]

having the diodes ensures that the charge time is governed by one side of the pot and the discharge time by the other without their interfering with each other. That way you can achieve a variable mark-space ratio (PWM). Plenty of great tutorials on 555 circuits online that will explain in even greater detail.

[@jarrinson29]

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?

[@basemgamal622]

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

[@insylem]

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?

[@toxanbi]

I perfectly understand your design. robot797 asked if he can use LM317 to controll an amount of light produced by LEDs. TheLawnWander said LEDs need PWM to do that. I have met a few people who mistakenly believe LEDs must be powered only in pulsed manner - otherwise LEDs will work in wrong mode. Bullshit. Actually, an amount of light produced by LED depends from current through it, so you should control current flowing through LED by any method you can do it, but not only by PWM.

[@jaapweel1]

I fully agree. UI accessibility can be really hard if you have to target people with serious disabilities, but color blindness is so easy to make allowances for, and so common, there's really no excuse not to.

[@EEVblog]

Did you watch the whole video?

[@AntonioDellaRovere]

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

[@ocayaro]

Bad form, Dave - modifying a circuit with the power on.

[@tennicktenstyl]

like 555 costs more than ¢15 lol

[@ocayaro]

Bartosz Olszewski It's the principle bro. Is power on? If "yes", turn off then modify.

[@tennicktenstyl]

Electro I know that and still I think it's not worth it.

[@ocayaro]

Bartosz Olszewski Would you eat without washing your hands? While you may not die, you are dicing with death.

[@tennicktenstyl]

Electro no, I wouldn't. But come on, I can't come up with proper analogy now, but he won't get any shock, maybe couple of cents if something got zapped. I understand that if you work with $1+/20V+ circuit it's good to turn off the power but for less than that I wouldn't even bother.

[@ch2o2]

hmm, nice PWM-hack but why not changing the brightness of the LEDs with the LM317, working in cc-adjustable-mode? Might be, the linearity of regulation gets lost but, heyy, much less parts to deal with ....totally wrong?

[@electrolysisresearch8013]

Can you help me to build a really high current PWM? Like 200amps would not need to be high Voltage only about 5v to 12v. All I really want to do is send 18KHZ 80% Duty cycle Square Wave doesn't even need to be Adjustable.

[@tkarlmann]

I'm not watching -- I got burned watching your fake April 1 555 foolishness -- so please keep your 555 circuits to yourself. I wasn't laughing then either.

[@akshi_az]

Doesn't that 9% minimum duty come from 1k resistor in series with charging diode? 1k/(10+1k) is exactly 9%

[@user-uk5bx1kz2k]

I think Mantis did 317 on purpose to supply stable current. remember old microscopes having bulbs? being relativly slow those can be PWMed without light flux pulsing. Don't get me wrong, pulsed leds are great for torch lights, but in my opinion they are bad for microscope backlight.

[@caddyguy5369]

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.

[@bernym4047]

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

[@Forssa1]

Simply adding a 50-100 ohm pot in series with the resistors on the existing regulator would have done it.

[@DemiGod3]

Can this chip NE555 use to drive a mosfet for the backlight circuit in a led tv? If your circuit can be used, what would be the output to connect to the gate of the mosfet and what value gate resistor? I think I should say it’s a Chinese tv but the PWM chip is defective so I just want to direct drive the mosfet for the backlight.

[@TheOriginalEviltech]

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.

[@metalmolisher666]

If i move my eyes fast i can also see neon tubes flicker at 50 or 100Hz. But 1khZ is impossible - your bain and eyes are much slower. Cars shouldnt have a frequenzy at all. THey are battery powered. ANd the battery is cahrged by the light machine. Cars should ahve 0 herz - so constant light. If u see flicker there i cannot explain it. Could it be that you close your eyes without noticeing?

[@TheOriginalEviltech]

I don't like that you use the 555 with the constant current regulator and you put a cap after it... That way when the 555 is in the lower % of the PWM the voltage over the power input of the new circuit will rise due to constant current regulator trying to keep the current at 0.5A. In that case the LEDs will be exposed to much higher peak current. They will probably survive it, but in time their crystals will start failing. I am not a big fan of PWM in lighting.

[@superdau]

Look up "Renard series". Basically it comes down to the fact that you don't really care (I choose arbitrary numbers here) if you got 900 or 950 Ohms, but you do care if it's 100 or 150! While the difference is the same, the ratio is quite different. So you choose values (starting with 1) where every number is the previous number times a constant factor, preferrably in a way that after a certain number of repetitions you get to 10 (so the whole series can repeat with just a zero added).

[@dalriada842]

Have you ever considered using coloured filters to help you discriminate between colours? Pause the video and hold a red filter up to the screen. The yellow trace will appear brighter, because of the red component. The reverse will happen with a green filter. Just a thought to aid your independence in these matters. I'm not colour blind myself, but it seems like it might work.

[@hefonthefjords]

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?

[@metalmolisher666]

Read the part where you talk about your keyboard. The sentence afterwards combined with the sentence where you say your keboard uses visible pwm frequenzys can be read like this. And yes i looked up how car leds work. You are correct on the leds. You never said what the trails u see look like. SO i imagines if they ahve a big gap it might be that you blinked with ur eyes.

[@WhitentonMike]

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.

[@rotlerin]

Great learning video Dave really enjoyed it ..................BUT.............a gross little hack thing covered in shrink sleeve dangling from a Mantis. Are you mad!!! You're an electronic genius and a mechanical Phillistine Dave. Stick the thing inside, drill the casting and stick the pot shaft out the hole with a nice knob on it. Beauty. Aesthetics Dave, Aesthetics.

[@metalmolisher666]

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.,

[@hefonthefjords]

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.

[@WhitentonMike]

The LED PCB power connectors should be the same on both sides. Just bypass the existing wiring from the jack to the PCB plugs. 2 555s and an XY pot would sure be cool and easy to use. There is the problem of where to run the wires to the outside of the case without modifying the case.

[@superdau]

The PWM version is more efficient. Yes, you still need the series resistor to limit the maximum current. But at let's say 50% duty cycle the resistor also only drops voltage 50% of the time. No current for the other 50%, no losses then (ignoring power needed by the 555)!

[@kckc9245]

Hi. I have a question how can i use the LM555 too get a square Wave on the output with a music sound input and adjustable speed. Thank you 👍

[@alexanderkuhn2298]

What would be the best way to control the pulse width using a microcontroller? Would the pot have to be a digital pot in order to work properly or can a microcontroller DAC simply output a voltage to this circuit somehow?

[@johnkerley4152]

I ca'nt find a lot of information on this type of pulse circuit. So I was wondering how well it works. I know that there are some lights that use this type of drive system. I wonder if the circuit you have would work well outputting 1 amp?

[@dalenassar9152]

How can you make a VOLTAGE-controlled PWM ? THANKS MUH

[@gotbread2]

I've a question about your 555 circuit. You connected the diodes to pin 7, and this pin with 1k to vcc. I prefer connecting the diodes directly to the output, gives a more symmetrical output and saves a component. Why choose this method?

[@TheBadFred]

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)

[@UberAlphaSirus]

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.

[@pjlegault6153]

A Power Potentiometer is an expensive part and will dissipate a lot of waste power as heat. Dave is in Australia so he is warm enough. By switching on and off to control brightness the design will be much more efficient.

[@bloomtom]

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

[@electroGoal]

Can we make buck or boost circuit with feedback using two 555 ic. Please reply

[@Pukkeh]

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

[@rayc5079]

What is the value of the capacitor between gnd and pin 6+2 ?

[@johncoops6897]

0u1 = 0.1uF = 100n

[@timramich]

I never said I could see 1 kHz. I don't know where you're getting this claim from. Cars LED tail lights use PWM because there is half brightness and full brightness. Half brightness is for running/tail lights, and full brightness is for brakes. You want to talk about impossible...one can't close and open their eyes fat enough to create the trails I'm talking about.

[@timramich]

They need a controlled current and controlled voltage. Voltage is easy. Since current is the number of electrons that flow in a given amount of time, you can see how PWM controls current, and does it more efficiently than anything else since it has an off state where no electricity is being used. A resistor just converts the current to heat.

[@timramich]

I don't get why people like car manufacturers choose to run such a low frequency for PWM LED control. Move your eyes quick and you can easily see the trails are broken from the pulsing. I just got an illuminated keyboard that also uses a visible-frequency PWM brightness control. Duty cycle is duty cycle whether its like 100 Hz or a few kHz.

[@rng8891]

I've used a couple of different CAD programs. Whenever I don't have a part I need to create it, and then put it into a library. Does anybody know where I can download DaveCAD libraries? XD

[@timramich]

Is that what the cars run for their tail lights? If I move my eye rapidly I can see the trail breaks up. They can't be running 1 kHz. But yeah, CRTs were hell for other reasons than flicker. My plasma's 48 Hz setting annoys me due to flicker, but that's common.

[@4dirt2racer0]

i noticed the transistor had casing molded around the back of it, does that ever interfere with the grounding? like do u ever have to sand them to get a more reliable connection? or am i totally wrong about that even.. does it Not also ground thru the back? i know, random ass question.. im just curious

[@Taylor_26GE93]

When monitoring the PWM signal between 16:40 to 17:00 there is a curve to the rising edge of the Square wave, what causes this? and how can it be prevented? Cheers, n Great video :D

[@metalmolisher666]

Of Course there are people who can see higher blinking frequenzoes or a bit further into the uv regine. But i would hardly doubt that you can see flashing lights in teh kHz regime.

[@Forssa1]

It wont be as linear as the PWM control though, but I think it'll be good enough for this.

[@MatrixOfDynamism]

do you know procedural C, object oriented C++, VHDL/Verilog, and any .Net languages? Do you know how to design USB device by writing its drivers (firmware and PC end)?

[@jlucasound]

$3,370. One has to be making money with that to justify the cost. Nice unit.

[@jlucasound]

$3,370. One has to be making money with that to justify the cost. Nice unit.

[@4dirt2racer0]

lol u said give the camera a reach around.. :p sry.. idk where tf that came from lol :p im certainly not prude but i usually try to keep it respectable

[@lukasandrysik]

Am I only one here who hates PWM regulated brightness? I see it everywhere - flashlights, LCD monitors with LED backlight, car tail-lights...It drives me crazy....

[@xDR1TeK]

Was trying to fiddle with a charge-discharge relaxation oscillator using single supply, didn't work, I have to do some hand calculations for it first.

[@pk2xw]

very easily 3D print a case using your maker bot and that case would just fit inside the square opening where the power jack socket is on the mantis head

[@ImaginationToForm]

Hi, Did have a question on the leds. Do they just look like they are lit at the same time since the voltage changing direction so fast? Thanks.

[@afivey]

I'm a beginner but this made me want to buy some 555s and pirate a DaveCAD licence. :D 17:13 - /watch?v=ZvCI-gNK_y4 (Musical accompaniment...)

[@metalmolisher666]

If u can see a 1kHz flicker u are a natural wonder. You wouldnt be able to watch tv. The old CRT monitors must have been hell for you.

[@Stefan_trekkie]

Add one more trans, npn. Before the 1.5 amp trans and this way will invert two ends, 99% will be available in ON duty cycle p.s. Sorry for my broken English..

[@WayneJohnsonZastil]

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.

[@TheBadFred]

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.

[@dumle29]

"should" - no "could" - yes if he wants to share his knowledge, it his choice, and would be a great gift from him. It's not his obligation tho.

[@toxanbi]

LEDs actually need controlled current source, not a controlled voltage source.

[@4dirt2racer0]

the plugs inside a device that shouldnt ever normally come apart seem kind of strange

[@robertbackhaus8911]

Note that if you are anywhere that honours US patents, someone holds a current patent on using PWM to alter LED brightness.

[@iStormUK]

DaveCAD HD (tm) uses SecuROM and Custom Firmware Dongle license to prevent copying. You can't fight the system! >:3

[@UberAlphaSirus]

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.

[@untitledblack7075]

After 8 years, KZbin:watch this boy....😁