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How to decrease the output current and voltage from this DC to DC converter?

Discussion in 'General Electronics Chat' started by Willen, Jan 5, 2014.

  1. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    That's pretty good really. Just one small thing, notice the other circuit had a 1k resistor on the output of the reference. So you have to move the 10uf cap to the left then install a 1k resistor from the top of the 10uf to the 1M resistor and non inverting input so it is just like the other circuit.

    The 4.15v measurement is at point A common to the battery negative terminal ( -Battery ).
    On the new schematic below, the 4.15v is between points A and B, and is measured when the battery is not yet fully charged.
    Of course if you set that to 4.15v then you must set the other voltage setting to charge the battery to around 4.16v or the voltage monitor LED may never turn on.

    You may not need the whole 10v, that's just there in order to have some value shown. You might be able to use 8v or 9v, but if the regulator gets hot then use a heat sink. The second LM317 can be a regular type in the original circuit but since you now use a TL431 you dont need it. You never mentioned that you also have TL431's on hand too.
     

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    Last edited: Jan 26, 2014
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  2. Willen

    Willen Well-Known Member

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    Wow first time I am listening (reading) such comment from an expert to me. Feeling like- I am also starting to became an expert :) hehe really.

    I thought R5, 1k is enough, but now I guessed (from your correction), I had to isolate opamp using additional 1k resistor for efficient feedback (1Meg).

    Yes I understood the operation. I will set 1st voltage 4.16V and 2nd voltage to 4.15V. I understood that comparator won't give ON output if it cannot get more than 4.15v (more than 1st voltage level). I think this monitor is very nice than before.

    I noticed that when battery is charging and when it is not charging I measured few milivolts changes, like- with charging- 3.97V but when not charging 3.95V (2mV up/down). Then I think I have to set 1st voltage to 4.17V and 2nd voltage to 4.18V (because real volt on battery is 2mV less).

    OK I will use 8V to get less heat. Sorry I even didn't know which parts are needed for monitor, so I didn't tell you about TL431. I have few pieces from old SMPS of PC, cell phone wall wart supply.

    May be I will post an entire schematic by combining current and voltage monitors to show you once. Thank you at all!
     
    Last edited: Jan 26, 2014
  3. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    Ok yeah if you draw the whole thing out that would be nice.

    Also i though i would mention that you can make a really really nice monitor using a microcontroller chip, even a cheap low end uC chip. I dont konw if you can get these but you would be very happy if you could, as well as a flash programmer to program it. Using the built in ADC you could monitor both the voltage and the current. That's what i do with my charger, and i have a readout that tells me what the voltage is AND what the current is. By looking at that, you know right away if it is done charging or close to done. So you may want to look into these chips to see if you can get any (not sure if anyone asked you yet).
     
  4. dave

    Dave New Member

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  5. Willen

    Willen Well-Known Member

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    I almost know nothing about digital electronics (PICs/microcontroller). But I always think that if I could handle that programmable chip, I would make make almost Anything!

    It took almost 2 years to understand basic analog electronics, learning from experts and web sites and few books. Recently I borrowed a engineering reference book for analog basic electronics. But I just heard only about microcontroller. I have no even basic concepts about it. I have no friends to help me here. I don't know where to start and what to learn. So I never thought about it.

    OK I will draw an entire diagram.
     
  6. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi again,

    Well let me ask you this then: Did you ever write a program of any kind in any language for the computer or other device such as programmable calculator?
    If you had any programming experience you would pick it up in a week most likely, but if not it might take longer.
    You did pretty well with the TL431 as a substitute for the LM317 so that's why i think you could pick it up fast enough. Not sure how much time you like to dedicate to this stuff either though.
     
  7. Willen

    Willen Well-Known Member

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    I just can write simple HTML codes hehe I bought lots of DVDs and CDs of C+, C++, Java, PHP, lotus and many more...... The disk has programming softwares and guides but they are teaching for advanced learner there. But I even do not no 'P' of programming. So I guessed it takes me long. But in future I like to learn C++, because it is very necessary I feel.
    Yeah, I am learning 'basic electronics' very well because I am learning it from American ex. engineers! :) I feel I had known few general concepts better than few engineering students of here (lower than 4th semester). So in Facebook, sometime I teach them deeply for their basic and small project if I found mistakes and can suggest. They have thought me an engineer hehehe but in real I NEVER learnt electronics formally.

    I feel so good to be engage with such stuff and I have huge interest in programming so had bought lots of programming DVDs but I even didn't knew that where to start and were to write codes. :) Just now as I said before I have to prepare for job. (I finished university degree and almost impossible to get job here, tension in mind. Thinking to do everything if I get job.)

    OK and At last I combined both current and voltage monitor circuit and made final schematics. I used LED1 around battery terminal to detect 'damaged or fully discharged' battery. If they connectecd here, LED1 won't glow due to full voltage drop.

    I used LED3 which truns OFF when battery charged fully (current less than 30mA approx). I hope I did better. I will show a next modify to ask few simple modification.
    For now here the final circuit-
     

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    Last edited: Jan 26, 2014
  8. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    That looks pretty good, with everything on one schematic we can see how everything works, and the extra LED looks interesting too.

    Just one small caution. If the battery voltage is say 2.00 volts the LED will not light i presume, but the caution is that a battery that reads 2.00v when it is NOT connected to anything like the charger may actually read high very very soon after being connected to the charger because the charge current could bring the voltage up very fast with a battery that is really bad. That means the LED will in fact light even if the battery was 2.00v before it was connected to the charger. A workaround may be to connect the battery before turning on the charger, but we should probably look at that in more detail first.
    Oh, did you mean to put the LED and R4 right across the cell?

    Since you have some programming exposure then i would think you should be able to pick up programming for say a PIC chip like the 12F675 for example. What makes it simpler is there are only something like 35 instructions to learn and most of them are simple operations on memory or reading an input or setting an output.
    A little tricky at first is how to set up all the require registers for the peripherals. What you do is start with an existing program and modify it to suite your own needs and then look into the reason behind some of the register set up coding.
    If you want to see this a little better look up the data sheet for the 12F675 PIC chip. You can always start a new thread about this too and im sure people here would be happy to help you get going.
    Just one small warning...once you get into these uC chips you'll wonder why you never did before, and you may never go back to pure analog again! No kidding. The technology is a complete game changer.
     
    Last edited: Jan 27, 2014
  9. Willen

    Willen Well-Known Member

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    Only few types of PICs are at capital city, I heared. I don't know which one is available and which one is not. Also 'programmer writer' is hardly available (or not). Few students are also saying to me same as you said- amazing PIC technology than analog. I just can imagine them...

    And at last, I tried another alternative- dual voltage monitor. LED3 turns ON if voltage level is in safe zone (0V to 4.14V). LED2 turns ON if battery starts to charge around danger zone (above 4.15V).

    I tried to add D1 (at output of LM317) as a reverse polarity protection diode for battery, but now I am thinking that it does nothing there.

    Please check it once what I made.
     

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  10. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    I guess you will have to check which PIC's you can get and if you can get a programmer or build one yourself. Im not sure i can recommend building one yourself but i know a lot of people have done it with great success in the past. You could ask people here that have done it, probably looking in the Microcontroller section here on ETO.

    If you use two LED's like that you probably want to make it so you can adjust each section voltage independently.

    Yes, D1 does not help in fact it actually hurts because it screws up the precise voltage set point which now depends partly on the diode temperature characteristics. A series diode almost never helps anyway for reverse polarity protection. It takes a parallel diode and fuse. The fuse goes inline with the power and the diode goes antiparallel to the battery cell.
    Interestingly, i am building this into my home power supply soon too. I just got the parts the other day (fuse holder, fuses, i had the diode).

    So you'll have to remove D1 and maybe add adjustments for the two LED's, and add an antiparallel diode if you feel up to it, maybe 1N5401 or similar along with a series fuse.
     
    Last edited: Jan 27, 2014
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  11. Willen

    Willen Well-Known Member

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    I am thinking to update myself to PIC. So I will do it in near future hope I can do it.

    OK I decided NOT to use protection diode, but what are you saying here- Adjustment for 2 LEDs? I am confused. Can't I make last circuit same as like this?
     
  12. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hello,

    Well if you want the two LED's to turn on for different voltages then you need to be able to adjust each voltage reference.
     
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  13. NorthGuy

    NorthGuy Well-Known Member

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    I am just wondering if you can order things from www.DigiKey.com? I think they ship everywhere in the world and shipping is very reasonable.

    You can also buy chips on eBay.
     
  14. Willen

    Willen Well-Known Member

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    It is just a simple solution but in real there are lots of problems. It's very hard to buy American components specially for Asian people. America is much more expensive area. For example in case of my country- If I got a job which is middle class for here, they will provide around Rs. 20,000 per month. If I converted this currency to US dollar it's just $200. May be it is little funny salary as a 'middle class salary' for Americans, isn't it? And digikey takes around $50 as a shipping charge, if I included components charge it might be more than $100. Once I visited digikey website, I found a normal trimmer caps which is rated $4. It means my currency Rs. 400. I think I can buy almost entire components for a simple small project here if I spent $4 here.

    2N2219 was rated also $4 there, but I bought 5 pieces of 2N2219 here at just a dollar. I can buy 10 pieces of 555 timer IC at just $1. I bought 40 pieces of BC547B at $1 here. All are working...

    And actually I even have no job till now. :)
     
    Last edited: Jan 28, 2014
  15. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    Wow that puts it into perspective why you have trouble getting parts sometimes. So the equivalent here would be someone making $4000 per month would have to pay $1000 for shipping! Now it becomes more clear.

    But since we are talking at least for the time being about the PIC line of microcontrollers, the company that makes them is called "Microchip", so did you try them? They have a sales site called "Microchip Direct". I say this because i find it hard to believe that no one else gets those chips in your area, so they must have some way to get them without a huge expense. At least you can try them and see what the shipping would be. They ship from Thailand, at least some parts. Good luck.

    http://www.microchipdirect.com/

    I dont know how accurate this is but here is shipping costs for various places:

    http://www.microchipdirect.com/ShippingInfo.aspx


    BTW what area are you in again? I can check with the local Post Office to see what they say would be shipping on a small package. I think you may have told me something about this before but i would rather check myself and see what the various options are. You dont have to give your entire address, just the general location so i can tell the Post Office. You can also PM me if you feel more comfortable with that.
     
    Last edited: Jan 28, 2014
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  16. audioguru

    audioguru Well-Known Member Most Helpful Member

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    It is a HUGE world.
    The middle-class income in a big city in Canada is 42 times as much as yours in Asia. But taxes, housing, fuel, clothing and food costs a lot more here. The taxes pay for most medical care and a pension for old people like me. Electronic parts are very inexpensive here.
     
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  17. Willen

    Willen Well-Known Member

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    Yes MrAl and AG !

    America has very high salary than here. So people of here trying to go there in America but it is hard! We need almost Rs. 20,00,000 ($20,000US) to go there and it's EXTREMELY high for middle class family. There each goods are expansive and also salary is high (same ratio). From here, few people have gone there and they are earning $2,000 per month there. Don't laugh at me because it's EXTREMELY high salary for here. And they known as very rich person here so they can get ANY girl to marry actually hehehe

    I live in Nepal now. I visited 'microchip direct' and clicked on Location list, they didn't have included my country. May be they've thought that we cannot buy from them hehe!

    Most of distributor has 'currier' as a shipping medium like DHL. It would be cheap little if they shipped through Post Office but advanced distributor won't send through post office. Once I found a distributor from Honkong they were saying they will send via post office from China post. First they said- "send money now as fast as possible, we will send your parts instantly." Then I said "I am a big distributor of here and want buy lot more components. This first attempt is just trial." Then they said- "We did hasty little for your payment, today I noticed that we don't have any crystals or crystal OSC module." I felt amazing, they had no complete components but were saying "send money just now as fast as you can." You know LOTs of fakes here in this part of the world. Almost I had lost my few dollars, which I collected hardly. :)
     
    Last edited: Jan 28, 2014
  18. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi again,

    Well they do ship to India with UPS and FedEx so there is a good chance they ship to Nepal too. You should probably contact them about this you may find it well worthwhile. India looks cheap enough too.
     
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  19. Willen

    Willen Well-Known Member

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    Yes, and I am trying to upgrade my life (life status) for these even cheap shipping rate and cheap components. Hope my dreams will come true...very soon... I will note these all sites, thank you lots!

    At least, I realize the value/importance of each and every single and tiny electronics components due to such unavailability of components. If found an IC or a transistor or any unique parts, it gives me a lots of happiness, may be you never got such opportunity to feel extreme happiness. :)
     
  20. audioguru

    audioguru Well-Known Member Most Helpful Member

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    I always feel happy. I feel extreme happiness a few times every day. My family gives me happiness. My pets also give me happiness. I am grateful that I am healthy and I have nothing to worry about.
     
  21. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    I used to feel very happy when my shipment of parts would come in, as i would be able to complete my project(s). These days it seem more of a necessity to order some parts so i'll still happy when they come in but now it is usually because i need them to fix something or improve something. So i guess im still happy but maybe not as much as before.
    For example recently i got some high current diodes and some fuses and fuse holder, and that was to fix and upgrade my variable bench power supply. It's the only commercial unit i have as i built all my other power supplies myself. It was on the expensive side but it has built in digital meters so it makes monitoring whatever is being powered easier.
    Also recently i had ordered a new alternator for the car. I was happy to see that come in 3 days sooner than expected except i was quite sick and it was really cold outside so i could not install it right away anyway. it took a couple weeks for a break in the weather and my flu or whatever it was before i could install it. So that was pretty much necessity's rule too.
     

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