I was scammed $4000 for R&D of a buck boost driver - Page 1
Forum section: electronics / general

author: bobhaha
author_rank: Contributor
timestamp: April 16, 2012, 05:14:21 pm
content: Hey guys,I'm new here and for one main reason... because I was scammed $4000 from an "Electronic System Engineer" from USA. He gave me a quote for $2300 for the reverse engineering and revision of an original buck-boost driver I had given him as a sample. Over a span of 6 months he asked for more and more money till we hit the $4000 mark at which point I said "OK THAT'S ENOUGH!". That is 260 hours worth of my hard earned money (I'm only 20 years old...). He then said that the contract we had was nulled because I couldn't cough up the dough to finish it. Now I'm stuck with nothing and I'm $4000 down. What has this world come to?Anyway... The good side of this story is, I've always been interested in electronics and have dabbled with some simple electronic projects (wireless door chime controlled light switch, open freezer door reminder, flashing light circuit with a 555 timer...etc). I think I have the capability to finish the project off but I will be needing some sort of guidance or mentoring. If anyone is willing to help me that would be awesome!I have already picked out a few IC's that I think would be good to use, but I need someone to check over my work. I have tried out the typical application model in LTSpice, but I'm not getting anything that looks like what I need.Is some one willing to give up a weekend and help me out? It would really mean the world to me!-Adrian

author: Lightages
author_rank: Unknown
timestamp: April 16, 2012, 06:29:45 pm
content: First of all let me say that I am sorry to see you getting ripped off. There are many scammers around the world and this is your hard lesson. A reverse engineering of something like a buck boost power supply should not take more than a day if the person knows what they are doing. Maybe it could take longer if the design used a proprietary controller IC but that is highly unlikely. This person took advantage of your naivety.I think you will find that any people will be willing to help with your design. Just post and wait for the criticism!

author: slateraptor
author_rank: Frequent Contributor
timestamp: April 16, 2012, 06:59:45 pm
content: Social engineering abounds.

author: Bored@Work
author_rank: Super Contributor
timestamp: April 16, 2012, 07:12:59 pm
content: It would be interesting to hear the other side. And it would be interesting to know why someone has a need to get a buck/boost converter reverse engineered. Someone who could spend $4000 at it, but previously rejected an offer for a $600 oscilloscope as being to expensive.

author: slateraptor
author_rank: Frequent Contributor
timestamp: April 16, 2012, 07:19:57 pm
content: Exactly my observation.

author: codeboy2k
author_rank: Super Contributor
timestamp: April 16, 2012, 07:36:05 pm
content: Quote from: BoredAtWork on April 16, 2012, 07:12:59 pmI'm kinda feeling like BAW here. I'd like to hear both sides too. Buck/boost converters are easy to design and controller IC's are a dime a dozen.TI, Linear, Maxim, Infinion, Panasonic, etc.. almost every manufacturer makes controller IC's and has application notes.Why anyone would need to reverse engineer one is beyond me.At most, characterize the one you have and design a new one with similar specs.Also, a point of note: contract engineering can be upwards of $100/hr and more. Just contracting 3 days of work at $100/hr can set you back $2400.At $150/hr it's $3600. If your engineer spends a week on it, then it's $4000 to $6000 dollars already. I'm not justifying anything here, just sayingthat an open-ended contract is never good, and it can get expensive very quickly.

author: bobhaha
author_rank: Contributor
timestamp: April 16, 2012, 08:23:00 pm
content: Hey guys, would just like to clear some things up. I was naive, this guy was feeding me all the things I wanted to hear. I now understand that I didn't even need the board reverse engineered, he just used it as a basis to earn my trust. I didn't do any research (and that was my downfall) into the project so I assumed he knew what he was doing, so lets go with what ever he says. If you saw the watermark on the contract you would piss your self laughing and throw it back in his face.... but he was extremely persuasive and again I was a sucker and believed every word of it.As for the o-scope, I was more after a cheap $200 max analog scope. So what was offered was, both too expensive and has a much higher capability than I need.As for posting what I have publicly, I'd rather speak one on one with some one if that is at all possible, just because posting my schematic online is basically an open invitation for others to copy my work. I know these are pretty simple circuits, but if it is at all possible, I would like to minimize the ability for others to copy my work.So if anyone is willing to help me one on one, that would be great.Thanks for your time.

author: tinhead
author_rank: Super Contributor
timestamp: April 16, 2012, 08:53:03 pm
content: hehe, let's summarize:- you have a project to finalize but you have no idea about what to do- you did spend already 4000$ to save your job/project (with 3rd party help) - without any result- you have no money left and looking now for idiots, ehm volunteer to help you out.- you running now out of time, the project owner/you boss is asking for results <-or-> you still dreaming aboutfast cars, girls smoking long cigarettes and what so ever (if so stop dreaming and start to work)my proposal - think about new job, playing @home with 555 flashing lights and real project are completlyopposite things. Start with something simple, e.g. learn some basics.

author: amspire
author_rank: Super Contributor
timestamp: April 16, 2012, 11:26:11 pm
content: bobhaha,If you do not want to show schematics, then if you describe the specifications we can at least discuss whether your design is something easy or something challenging. Truthfully, if it is easy, it will hardly matter if anyone sees the design or not. If they want to make a copy, it will not be hard for them to make a copy.Some designs for switching supply's are almost trivial with the modern IC's, but other designs can be extremely challenging, and could easily take a $40,000+ design job.Even with a very simple design, there can still be a fair amount of work taking it to production - checking for the effects of component variation, getting the board layout right, thorough testing.At the moment, we do not know, so we cannot really help much.You could try going to the NS/TI Webench site and see what design they offer:http://www.ti.com/ww/en/analog/webench/power.shtmlRichard.

author: BravoV
author_rank: Super Contributor
timestamp: April 17, 2012, 02:18:37 am
content: Leave that drama alone, nobody is interested and also it sounds so retarded.Now lets move the discussion on what kind of help do you really need "specifically" in your thousands dollars project ?Grabbing someone's weekend to commit in helping you is not just good enough, you must tell the complete story.

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 17, 2012, 04:24:05 am
content: Quotea good lesson for me as well. now, is this called... false economy? if i foresee $4000 will be spent. i'd rather it'll go to agilent "Infinity Vision" X000X.

author: EEVblog
author_rank: Unknown
timestamp: April 17, 2012, 05:30:45 am
content: I think it may be hard to get someone to help with your personal project if it's not done in public.People on forums like this like helping in public because knowledge gets shared, many people learn new things, and the info is always there for when someone else comes along with the same or similar need. And you benefit too because you can have more than one person contribute, critique, and offer suggestions, which is kind of what got you into the trouble in the first place, you trusted just one person and they didn't come through for you. Do you want to trust the one person again?I'm not sure what's so propriety about a switchmode converter that you need to keep it private for anyway? You don't need to tell us the applications, just the PSU specs and what you are trying to achieve.Dave.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: April 17, 2012, 07:31:31 am
content: OK, reading between the lines, I think I have seen this situation before. I used to work at a university affiliated research lab many decades ago. Periodically would-be "inventors" with no technical acumen would darken our door and ask us to finnish their "precioussss..s". One case was a nice lady who had a semi plausible idea: it was for a car trip computer for business folks who needed to keep track of mileage and such for tax purposes, it would be wired into cars aftermarket component style. Her problem was that her family had money and she had fallen in love with her idea and it had some quirky and expensive requirements like a printer. The last I heard of her was that some private engineering firms had made impractical prototypes and cleaned her out of around $200K, (back in the 80s!). Another guy was someone I knew from high school. He had the dream of a compressed air powered piston car, I repeatedly tried to inform him of the laws of thermodynamics but he figured he could drive for free, no gasoline, and that we science guys were "too negative". Another case- one day we get a phone call, the receptionist hands the receiver to me:*abridged conversation*"Hi, I've invented this thing and like I need a patent or something"There elapsed a minute or so of dancing around what the thing-a-ma-jig was as he was worried I might steal it. I told him I needed to know the basics of what it was."OK, its .. its a camera that weighs stuff."me: "how?""You point it at something like a refrigerator and it weighs it, without lifting it. You can design that for me and I get the patent""you're not going to steal my idea are you?"me: " no, there's no danger of me stealing that. You can only figure out how much something weighs from its dimensions if you first know its density""Density? whats that? ...."There was an awkward pause while I tried to formulate an explanation and exit plan so I could get rid of this simpleton, remember I was young and polite in those days.he pre-empted " Ya density!, .. you can make my camera see density !"me: "no, I don't think we can do that sir."

author: G7PSK
author_rank: Super Contributor
timestamp: April 17, 2012, 08:03:50 am
content: As the owner of an engineering company I have come across the density problem myself, the density problem really lies between the prospective customers ears. I try to tell them that the problem cannot be solved realistically either down to cost,weight or just not possible or safe but they still think they have this marvelous idea that will make them millions if I can only invent/engineer it for them. I always try to let them down gently but sometimes the reaction to being told that it is not viable is quite hostile.

author: Bored@Work
author_rank: Super Contributor
timestamp: April 17, 2012, 08:10:08 am
content: Quote from: chickenHeadKnob on April 17, 2012, 07:31:31 amWho hasn't? Complete with offerings of 10% shares in an imaginary company, about to be worth many millions if things work out.Am I the only one thinking that the first posting and the later explanation don't add up? First there needs to be something reverse engineered, i.e. he is looking to get someone else's work copied . Then suddenly some schematic, his schematic, exists, and he is worried someone copieshiswork.

author: EEVblog
author_rank: Unknown
timestamp: April 17, 2012, 08:46:44 am
content: Quote from: G7PSK on April 17, 2012, 08:03:50 amNeedless to say, I'm easily found on internet searches, and hence get these kinds of requests all the time!I do try to be as polite as tactful as possible...They usually start out with something like this - "I have this brilliant idea that will be worth millions, I've done the math and I know the market, but I lack the electronics knowledge required, and that's where YOU come in! Working together and pooling my idea with your expertise, I know we will be a massive success! yarda yarda yarda..."Dave.

author: nukie
author_rank: Frequent Contributor
timestamp: April 17, 2012, 09:11:10 am
content: You paid a hefty amount of money for reverse engineering of a power supply and now you are worried that someone copied your circuit?Are you worried that your boss finding your work here? or is this a university assignment?I can't think of a psu design that needs to be protected unless you have found a way to design a 99.999% efficient circuit.

author: AntiProtonBoy
author_rank: Frequent Contributor
timestamp: April 17, 2012, 09:14:58 am
content: Re. estimating an object's density remotely, the closest engineering solution I can think of is some sort of x-ray imaging technique.

author: BravoV
author_rank: Super Contributor
timestamp: April 17, 2012, 09:25:15 am
content: Quote from: EEVblog on April 17, 2012, 08:46:44 amSome points missing Dave, additions in bold to make it sounds more realistic.

author: bobhaha
author_rank: Contributor
timestamp: April 17, 2012, 10:45:52 am
content: Alright, I'll explain in more detail. The point at which I had told the scammer "THAT'S ENOUGH" was about 2 months ago. I am now working on this project my self, reading up on all sorts of things, feed back loops, burst mode etc.. figuring out what all these terminology means. The "engineer" (I use that word loosely) convinced me he needs to reverse engineer another similar product in order to come up with a solution to my project.As for the schematics, personally I feel like I should be protecting them / hiding them, just because I don't want to see my same design copied and some other company undercutting me cause they have the ability to buy in 10,000 units. But I want to see this project succeed and if you guys are kind enough to help me, then I'm happy to post what I have so far publically. Also I understand how the public-ness of an idea can help others... which I didn't think of... So I'm happy to do that too.Anyway... Here's the explanation... I work with lasers (check out my sig) and if anyone has worked with them before, you would know that they are susceptible to voltage spikes and current fluctuation, so a driver is needed to smooth out the raw DC voltage and give the user a constant current to the diode. The current laser diode (LD) driver is only able to reach a max of 1.5A output but needs to be very well heatsinked in order to reach those currents. Needless to say that impacts battery life... it's just wasted energy.For my design I wanted to get to 2-2.5A output (max) with minimal to no heatsinking. The next best thing on the market is 58% efficient and can only reach 1.8A. I also need a 2-5.5V output. Regulation Ripple (4-100kHz) should be < 1% and should be able to run off 2-4 AAAs, AAs, Cs, Ds, and single lithiumbatteries primary and rechargeable.Annnnnd that's it. Stand by for the current schematics I have...EDIT: this is what I'm working on in LTSpice... but not getting very far...

author: Psi
author_rank: Super Contributor
timestamp: April 17, 2012, 11:35:15 am
content: Quick search on digikey came up with a LM2623- Good Efficiency Over a Very Wide Load Range- Very Low Output Voltage Ripple- Up to 2 MHz Switching Frequency- 0.8V to 14V Operating Voltage- 1.1V Start-up Voltage- 1.24V - 14V Adjustable Output Voltage- Up to 2A Load Current at low Output Voltages- Up to 90% Regulator EfficiencyIf you want absolute smooth output you might have to go with a tracking boost regulator followed by a linear regulator .

author: Unknown
author_rank: Unknown
timestamp: April 17, 2012, 11:43:03 am
content: Quote from: EEVblog on April 17, 2012, 08:46:44 amOne wonders whether or not your response would have been different if the poster wanted to go open source?In academic circles people with wide audience, like yourself, often act as communicators linking right projects with right people even if they don't contribute personally. It is none of my business really but dissing your communication publicly without mentioning anyone in particular won't be much help in that direction. It won't put off the thick and the frauds but the remaining folk might start asking themselves "Is it a good idea to go to Dave with this? Maybe he is not the right person to go to with new ideas?" my 2c.

author: EEVblog
author_rank: Unknown
timestamp: April 17, 2012, 12:01:17 pm
content: Quote from: BravoV on April 17, 2012, 09:25:15 amAh yes, I stand corrected!Dave.

author: bobhaha
author_rank: Contributor
timestamp: April 17, 2012, 12:04:15 pm
content: Quote from: Psi on April 17, 2012, 11:35:15 amSorry I might be missing something here... But isn't that a boost converter? Or can it be used in a buck boost config too?I did however notice it can be used with1, 2, 3 or 4 Cell Alkaline Systems1, 2 or 3 Cell Lithium-ion SystemsWhich is great! But there is no mention of when Vin > Vout

author: EEVblog
author_rank: Unknown
timestamp: April 17, 2012, 12:12:26 pm
content: Quote from: bobhaha on April 17, 2012, 10:45:52 amDo you actually need a constant voltage or a constant current output?You mention the diode needs a constant current, but you are specifying a voltage output here.And I also presume that the output voltage could be eitherabove or belowthe input voltage?In which case you should probably be looking at a SEPIC type solution, likely with an external switch to get the 2.5A required.Also, what actual range of output current do you need? As almost any switching regulator is going to have a peak efficiency at a certain current, which drops off either side the peak. i.e. it could be 95% at a designed 2A, but only 70% at 1A.My first thought would be looking at LED drivers. There are countless battery powered constant current LED torch solutions around.Dave.

author: Bored@Work
author_rank: Super Contributor
timestamp: April 17, 2012, 12:22:11 pm
content: So he finally managed to get people working for him. What about a 10% share in his company?

author: bobhaha
author_rank: Contributor
timestamp: April 17, 2012, 12:57:15 pm
content: Quote from: EEVblog on April 17, 2012, 12:12:26 pmI need it to be constant current.The idea is for the end user to replace the current set resistor and that will give them a specific current. As for the LED drivers many which have been tested, have a tendency to not filter the output voltage spikes enough and that will be detrimental to the diodes lifespan.As for the output voltage, yes Vout can be higher or lower than Vin.. thus the need for a buck-boost configuration.-Adrian

author: Psi
author_rank: Super Contributor
timestamp: April 17, 2012, 01:02:26 pm
content: Quote from: bobhaha on April 17, 2012, 12:04:15 pmsorry, yes, you're right, for some reason i thought you only needing stepup.

author: bobhaha
author_rank: Contributor
timestamp: April 17, 2012, 02:10:33 pm
content: That's fine, I appreciate any and all help.The IC's I have been looking at in terms of price and functionality are:TCP63020http://www.ti.com/lit/ds/symlink/tps63020.pdfandLTC3533http://cds.linear.com/docs/Datasheet/3533f.pdfBoth of which I think might work. I have posted my schematic of the LTC3533 but when I run that in LTSpice I'm getting nA output... any reason that is standing out that could be causing this problem?

author: EEVblog
author_rank: Unknown
timestamp: April 17, 2012, 02:15:35 pm
content: Quote from: bobhaha on April 17, 2012, 12:57:15 pmAnd that will change the efficiency, of course.Usually you design a switching supply optimised for a specific current, and if you need to change it easily, you have to live with lower efficiency at the other currents.QuoteSo filter it some more?Dave.

author: bobhaha
author_rank: Contributor
timestamp: April 17, 2012, 02:29:53 pm
content: Quote from: EEVblog on April 17, 2012, 02:15:35 pmI understand that, but as long as it is efficient in the top end of the current scale, that will be the winner. Low efficiency on low output currents is not going to be as detrimental to battery life than low efficiency at high output current.I forgot to mention as well, this is for amateur / hobbyists, I am not a company or going to sell thousands of these.-Adrian

author: Time
author_rank: Frequent Contributor
timestamp: April 17, 2012, 03:39:41 pm
content: You're only 20 years old. Get an EE degree and some more life experience before taking on such endeavors.

author: Short Circuit
author_rank: Frequent Contributor
timestamp: April 17, 2012, 04:49:03 pm
content: Quote from: Time on April 17, 2012, 03:39:41 pmStupid advice, 20 is perfect age; plenty of life ahead to either enjoy the benefits of your choices, or to make up for the failuresTalking like this leads to long and boring Joe average lives, always ready for an excuse not to take some risk

author: Rufus
author_rank: Super Contributor
timestamp: April 17, 2012, 04:56:24 pm
content: Quote from: EEVblog on April 17, 2012, 02:15:35 pmI have designed some laser diode drivers and they are a pain in the arse.Specs for one diodeRated power output 10mW continuousAbs Max power output 11mW for 10us.Efficiency spread (power vs current) - about 3:1.Not all are that fragile but many are specified to operate on the edge of self destruction. The optical power density in laser diodes can be incredible, over 10MW/cm^2.You have to be so careful that the driver is well behaved under all possible conditions.

author: free_electron
author_rank: Super Contributor
timestamp: April 17, 2012, 05:42:57 pm
content: LED drivers are the wrong approach for laser diodes.... laser diodes are waaay to sensitive to voltage spikes...Make a sepic pump that gets you at a suitable voltage for your laser stack. ( roughly 1 to 1.5 volts more than what you need )Follow that by linear current source ( classic opamp / transistor current sink). ( hence 1 to 1.5 volts extra. this gives the current sink enough 'breathing room' )Add a startup lock so that the regulation always ramps up slowly ( can be done with a simple r/c network that influences the feedback node of the current sink. )programming the output current can be a simple resistor. ( set the control voltage of the current sink. )look for a sepic control chip that can make the suitable output voltage. most likely you can find a 6 or 8 pin chippie. littel inductor , fast schottky diode and you are golden.a good opamp like a op27 followed by a power transistor style BD239 will do the rest ...

author: bobhaha
author_rank: Contributor
timestamp: April 17, 2012, 06:06:34 pm
content: Quote from: free_electron on April 17, 2012, 05:42:57 pmPerfect, this is the info I am looking for...LD's are very fragile. But the specs I have listed before are known to work and this is what I need. Sorry for my ignorance, but how small are these components? I would like these to either fit on a round 16mm disc PCB or on a 9x12mm board.Has anyone given my schematic a glance? Any ideas?

author: Time
author_rank: Frequent Contributor
timestamp: April 17, 2012, 08:05:38 pm
content: Quote from: Short Circuit on April 17, 2012, 04:49:03 pmIf a person is stealing someone else ideas and acting like they are his own and than walking away like its ok - its perfect advice. Its not like he has a multimillion dollar original idea here. He hired someone to reverse engineer something a 3rd year EE designs for homework and than called it R&D. Someone like that isn't going to change the world, sorry.

author: bobhaha
author_rank: Contributor
timestamp: April 17, 2012, 08:18:38 pm
content: Wait, wait, wait...I don't know if you read the whole thread, but that is not what I did. I explained a while back that the "engineer" ( using the word loosely) lead me to believe that, to create my projects solution he needed to reverse engineer another design. I thought this was common practice, till I got scammed and set out to finish the project that I started.I had no intentions of copying anyone. I was merely giving the "engineer" a baseline, meaning I want all the features this device offers, plus the added features I require.Does that make sense? Not sure if I'm explaining it right... I don't want people thinking, I'm trying to copy anyone or steal any ones ideas. I was purely asking for a new design of a common driver from the engineer and was lead to believe that the course he took was industry standard.-Adrian

author: free_electron
author_rank: Super Contributor
timestamp: April 17, 2012, 09:28:44 pm
content: right. give me some more info on the laser stack. how many diodes ? what is the voltage drop across the stack ? what is the maximum current through the diodes ?16mm disc.. doable. it'll be a tight fit , parts on both sides.

author: IanB
author_rank: Super Contributor
timestamp: April 17, 2012, 09:38:40 pm
content: Quote from: bobhaha on April 17, 2012, 08:18:38 pmEngineers often or always look at other people's designs for insight and inspiration. But they do so from a position of prior knowledge and understanding to see if they missed something, to see how other people approach the problem.Whenever you engage someone to design something for you, the first thing you need to do is to evaluate whether they know what they are doing. So for a power supply for laser diodes they need to be able to explain what the typical constraints and requirements are for such a supply (tightly regulated current, no overshoots, no spikes, fail safe features on start up and shut down, that kind of thing). Preferably they need to show credentials where they have designed such supplies before. On your part, you need to have done your research so you can properly evaluate your consultant. You need to know what questions to ask.If your expert's first reaction is, "I need to take an existing design apart to see how it works", that should be a big red flag to you. It would be like asking an architect to design a house for you who has never designed a house before.Also note that if you want something apparently reasonable, but which apparently doesn't exist on the market already, there might be some hidden reasons why such a thing is hard to build. Can there really be nobody who has wanted such a thing before?

author: onlooker
author_rank: Frequent Contributor
timestamp: April 18, 2012, 01:49:28 am
content: Am i missing the obvious? The OP's schematics is no more than the one (reference design) showing in the datasheet of LTC3533, except with a wrongly added R7. The R7 is also the reason the OP got not current flow and I am puzzled as to why the OP did not see it.

author: IanB
author_rank: Super Contributor
timestamp: April 18, 2012, 02:05:50 am
content: Quote from: onlooker on April 18, 2012, 01:49:28 am'Cos the OP doesn't know anything about electronics? It's really weird how the people who have the least expertise are the people most worried about people copying their "work". It happens a lot in the software field, but apparently is not confined to that arena.

author: gregariz
author_rank: Frequent Contributor
timestamp: April 18, 2012, 03:17:19 am
content: Quote from: IanB on April 17, 2012, 09:38:40 pmThere was a column about this in a recent elektor. Its unreasonable to expect someone to know the practical design pitfalls of every circuit topology so the solution as mentioned in that column is that 'getting up to speed on something' should be outside of any contract. ie. generalists/consultants should be able to put together enough skills to reliably design as long as a customer doesn't expect cutting edge performace. ex. There are engineers who spend their lives just making the best passive low pass filters, but assuming that your requirements are non-critical any decent RF engineer should be able to make sensible enough construction choices as he's coming up to speed in order to get something satisfactory to work.Ideally you also want a fixed price contract for goods delivered, so you are not paying hourly costs. Equipment and physical development costs however should be outside of any negotiated fee for service.

author: cybergibbons
author_rank: Frequent Contributor
timestamp: April 18, 2012, 06:31:35 am
content: Why have so many of us worked on laser power supplies?There are so many things to catch you out. I wouldn't approach it as a first project - I worked under someone extremely experienced and found it challenging.

author: EEVblog
author_rank: Unknown
timestamp: April 18, 2012, 07:26:23 am
content: Quote from: bobhaha on April 17, 2012, 02:29:53 pmEDIT after having read your recent post:And you paid thousands to have a circuitreversed engineeredprofessionally designed for a hobby project??Dave.

author: Bored@Work
author_rank: Super Contributor
timestamp: April 18, 2012, 08:17:04 am
content: Quote from: EEVblog on April 18, 2012, 07:26:23 amBut didn't want to pay more than $200 for an oscilloscope ... Did I already wrote that things don't add up for me? I guess I did.

author: bobhaha
author_rank: Contributor
timestamp: April 18, 2012, 02:52:58 pm
content: Quote from: EEVblog on April 18, 2012, 07:26:23 amBecause I had the money and not the experience/knowledge. These are fairly simple circuits, it's just no one in out niche hobby knows how to create such a circuit.@ BoredAtWork, What car do you drive? Why didn't you buy a Ferrari instead? Yes it's more expensive, but it can go faster and has better acceleration etc...The reason why I didn't go for anything more than a $200 scope, is because I don't need anything more than what a $200 scope can provide me. At the time I needed a 2 channel scope with about 25-50MHz range on it. That's it... I don't need a Ferrari to just drive the the shops and back... get it?

author: bobhaha
author_rank: Contributor
timestamp: April 18, 2012, 03:12:37 pm
content: Dunno what you're talking about

author: free_electron
author_rank: Super Contributor
timestamp: April 19, 2012, 01:02:39 am
content: right. enough with the cannon fodder. can we get back to the technical bandwagon ?the laserdiodes being used : are they 'naked' laser diodes or do they have the compensation buitlt in ?normally a laser diode is a 3 or 4terminal device. the second part is an optical pickup that tells you what the diode is emitting. this is used to control the drive current.if your laser diodes is a 2 terminal device it means the compensation is built in and we don't need to take care in our linear stage.

author: Psi
author_rank: Super Contributor
timestamp: April 19, 2012, 02:27:39 am
content: Quote from: free_electron on April 19, 2012, 01:02:39 amAll of the metal can type laser diodes have 2 wires out the back with the exception of packages with multiple diodes.Ya can't tell if it has optical pickup by the number of terminals present.The pinout varies greatly, any combination of the two terminals plus the case can be used for the laser diode and optical pickup (if present). Often there are terminals with no connection at all.

author: bobhaha
author_rank: Contributor
timestamp: April 19, 2012, 09:38:53 pm
content: Most of the diodes we use are 3 terminal devices.There is a Positive, Ground and Case pin.Case pin is not used. It's isolated from the other pins and is only used as a voltage "pick up" point.There is no need for optical pick up.User just needs current control... designated by the current set resistor.This is a constant current driver... meaning it will output a constant current and the diode will pull what ever voltage it needs from the driver.

author: bobhaha
author_rank: Contributor
timestamp: April 25, 2012, 01:18:59 pm
content: Bump...Ok so after playing around with the typical application model... I've got this...One thing I would like to ask is how can I change it to be in constant current mode? I have read through the Datasheet a few times and I need to change the values on Vo. But can someone explain how this is done so I can test with LTSpice and try to improve from the typical application model.-Adrian

author: free_electron
author_rank: Super Contributor
timestamp: April 25, 2012, 03:14:18 pm
content: That chip is not suitable for your design. Max vout is 5.25 volts. Your stack of laserdiodes needs more than that.Also , current mode regulation with this thing os difficult as it has internal current sensing...

author: M. András
author_rank: Super Contributor
timestamp: April 25, 2012, 03:41:08 pm
content: hmm now the user needs, this tells me this isnt a hobby project or it is but for selling

author: bobhaha
author_rank: Contributor
timestamp: April 26, 2012, 06:48:46 am
content: Quote from: M. András on April 25, 2012, 03:41:08 pmI don't know what that means... but if you don't believe me, here's my thread on the subject started on 14-08-2011.http://laserpointerforums.com/f44/new-boost-driver-dev-66195.htmlQuote from: free_electron on April 25, 2012, 03:14:18 pmI understand that. I technically need 5V max output... but was aiming for 5.5V to give a bit of overhead room to move. Any suggestions or links so I can understand the basis of setting the output voltage?Do you think something like the TPS63020 would be better suited for this application?http://www.ti.com/lit/ds/symlink/tps63020.pdf-Adrian

author: BravoV
author_rank: Super Contributor
timestamp: April 26, 2012, 07:28:10 am
content: With your ambition there, I'm quite surprised that you don't even understand the basic concept of constantcurrentmode orcurrentcontrol loop.Have to admit that I never toyed with laser diode, but I "assumed" that laser diode basically is like ordinary led diode that needsconstant regulated currentinstead of voltage, and it looks like you keep doing these meaningless and randomly testing various "voltage" regulators that will not get you even close to the final product in maintaining a precise current mode that you needed.Also dropping a voltage with a resistor in series with the laser diode in order to get the right current while in voltage regulation mode is not the best method, especially you're looking for power efficiency and the main power source from small form common batteries.Again, this is just my brief observation, correct me if I'm wrong.Not sure if this fits for driving the laser diode, since you're familiar with Linear LTSpice, these examples are Linear made regulators designed specifically for drivingconstant current devicelike high power led, LTC3454 or lower power LTC3490.

author: bobhaha
author_rank: Contributor
timestamp: April 26, 2012, 03:25:03 pm
content: Quote from: BravoV on April 26, 2012, 07:28:10 amI'm not sure if you have read the entire thread or not, but the reason why I am blindly testing out values/models is because I have only a little bit of knowledge in this field. This is why I am asking for a little bit of help here.Neither of those LED drivers will work. I need adjustable (set resistors) control over the current up to 2A.Is any one willing to help me out? Surely it can be done fairly quickly if all prior research is done.

author: Obi_Kwiet
author_rank: Regular Contributor
timestamp: April 26, 2012, 10:28:19 pm
content: Alright, I just saw this thread, and I thought I would weigh in.I've spent the last few months working on a very similar project that I'd like to sell on LPF, and I just finished ordering the components for my first prototype this morning. I recently graduated with an EE degree, but I haven't taken any power electronics courses and I decided that this would be a good project to teach myself a little about SMPS.I'm not trying to discourage you here, I think it's a good thing to try, but I feel that you are going about it the wrong way and you are overvaluing your services. This should first and foremost be a learning experience. It is simply not realistic to expect to come up with a design that is better in every way than everyone else who is more experienced and more educated than you on your first try, so you should accept that so that it doesn't negatively impact your learning experience. There is no point in even trying if you aren't willing to learn. You should start with a power electronics textbook. You may not understand everything, but you should be able to pick enough to work with.Secondly, "design" is going to be used rather loosely in this context. You are basically implementing a chip's reference configuration straight out of the data sheet with some tweaks. In my converter, I added a current control loop with another IC, and an IC to add under-voltage protection for the Li-I batteries, but for the most part, the vast majority of the design is done by TI, or NI, or what ever company you source your main IC from, so it's pretty pointless to get too secretive about "your" design. The hard part is looking at all of them and finding the most optimal one for your desired specs. I spent weeks reading through data sheets, which was boring, but a very good learning experience. There were several times that I thought I had found my IC, only to have to start over when I realized that it just wasn't quite what I was looking for. I must have looked at just about every LED and generic switch mode IC that supported a topology that would output voltages both above and below the input voltage. Again, it's a learning experience. Don't be impatient. Hell, I'll even tell you which chip I used. It was the TI TPS 63020. It was my final choice for a variety of reasons, and I found out about a week ago that that a few other people at LPF have already built driver based on that IC.http://laserpointerforums.com/f67/tps63020-based-driver-70311.htmlI was a little disappointed to learn that someone had already built something based on that IC, but again, it just goes to show that there's no point being afraid of someone copying you. You are basically just implementing ICs. My own "design" is unique in the specifics of its implementation, and I'm hoping it will perform better than his did, but I won't know that until the parts show up.On the technical side of things, a lot of drivers, including the TPS63020 have current control loops, but you can't actually program the current, they are only there to protect the chip from getting fried. I had to add a current control IC, which should in theory work, but there is a lot of EM stuff that I have no way of addressing analytically which could throw a wrench into it. Remember also, that an IC's quoted efficiency is the peak efficiency it could get in the ideal case. If its max current output is 2A, and you are pulling 2A from it, you might not even be competitive with an LDO in that case. Part of the reason I choice the TPS63020 is that it has really good documentation of its efficiency curves. Remember too, that you will have to do a PCB layout. That will also take some learning. If you want to sell in bulk, you have to factor in all the different start up costs, the costs of doing assembly on a board that will probably have components on both sides, and shipping of all the intermediary pieces, and the costs of having sub 100% yields. It all adds up, and you have to design around it all. If you are just looking to make a big profit, this is the wrong place to try. LPF has a lot of people who are just trying to contribute to the community, who are just selling stuff to cover their costs, and even then, they end up putting in a lot of work for free.And as a note to those who say you need to use an LDO to drive a laser, yes you probably should, but this is for enthusiasts who are trying to push the envelope, not for commercial products. I don't think that there is any way to fit a tracking pre-regulator onto the preferred 16mm diameter board when if you want a 1.5A+, current controlled output, so it's just a necessary tradeoff if you want to greater efficiency.

author: bobhaha
author_rank: Contributor
timestamp: April 29, 2012, 06:03:31 am
content: Quote from: Obi_Kwiet on April 26, 2012, 10:28:19 pmIf you read the thread... I actually did find and use the TPS60320 but I was getting very inconsistent output from LTSpice. I'm not scared to post my schematics online ( I already have...) I just need someone to give me a hand. Are you willing to help me out? I am not in it for the money... but recovering the money I have lost would be help.PS: What's your LPF username?

author: Obi_Kwiet
author_rank: Regular Contributor
timestamp: May 01, 2012, 02:32:43 am
content: I must have skimmed the part where you mentioned that. My LPF user name is ObiKwiet. I'd be happy to give you some pointers about how to go about doing this project. I think maybe LTSpice is going to be the sort of tool that is going to be too difficult to get meaningful results from at this point. Who knows how well TI's model is going to work on Linear Technologies circuit, and worse, who knows how close those results will be to real world performance.I think ultimately, you are going to have to sit down and put a little effort into learning how SMPS work at some level. Like I said before, a lot of chips will require an external sense resistor and an instrumentation amplifier of some sort, the configuration of which will will have to be designed for the chip you are working with.Do you have any specific areas you want help with?