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I am a professional electronics and computer systems designer so keep shooting guys!
  • ranjeevm commented on Elecrow's instructable Remote control via GPRS/GSM SMS(Arduino)2 months ago
    Remote control via GPRS/GSM SMS(Arduino)

    I see no point doing this project unless you have these parts lying around because you happen to be an Arduino and Electronics hobbyist. Here are the reasons:1. There is another project on this website that achieves the objective in <$50 (search for "start your car from a cell phone via GSM relay" on instructables)2. The same project has an idea of a very simple interface to the car. Simple is beautiful indeed!!3. You can control up to 7 car functions (if the need be)4. You do not have to be a software wiz at all. You do need to be a hardware wiz either if all you need is to start the car (to do more look my addition in the comments)5. I don't see the author being too interactive / helpful. No blames just stating facts6. You may easily be able to start a lamp with this proj...see more »I see no point doing this project unless you have these parts lying around because you happen to be an Arduino and Electronics hobbyist. Here are the reasons:1. There is another project on this website that achieves the objective in <$50 (search for "start your car from a cell phone via GSM relay" on instructables)2. The same project has an idea of a very simple interface to the car. Simple is beautiful indeed!!3. You can control up to 7 car functions (if the need be)4. You do not have to be a software wiz at all. You do need to be a hardware wiz either if all you need is to start the car (to do more look my addition in the comments)5. I don't see the author being too interactive / helpful. No blames just stating facts6. You may easily be able to start a lamp with this project but starting a car is a different ball game. Wiring has to be deciphered, car security needs to be overridden!

    I see no point following this project unless you have these parts lying around because you happen to be an Arduino and Electronics hobbyist. Here are the reasons:1. There is another project on this website that achieves the objective in <$50 (search for "start your car from a cell phone via GSM relay" on instructables)2. This project has an idea of a very simple interface to the car. Simple is beautiful indeed!!3. You can control up to 7 car functions (if the need be) 7 >> 4!!4. You do not have to be a software wiz at all. You do need to be a hardware wiz either if all you need is to start the car (to do more look my addition in the comments)5. I don't see the author being too interactive / helpful. No blames just stating facts6. You may easily be able to start a lamp...see more »I see no point following this project unless you have these parts lying around because you happen to be an Arduino and Electronics hobbyist. Here are the reasons:1. There is another project on this website that achieves the objective in <$50 (search for "start your car from a cell phone via GSM relay" on instructables)2. This project has an idea of a very simple interface to the car. Simple is beautiful indeed!!3. You can control up to 7 car functions (if the need be) 7 >> 4!!4. You do not have to be a software wiz at all. You do need to be a hardware wiz either if all you need is to start the car (to do more look my addition in the comments)5. I don't see the author being too interactive / helpful. No blames just stating facts6. You may easily be able to start a lamp with this project but starting a car is a different ball game. Wiring has to be deciphered, car security needs to be overridden... that's complicated and being an arduino expert may not help there at all!!

    I see no point doing this project unless you have these parts lying around because you happen to be an Arduino and Electronics hobbyist. Here are the reasons:1. There is another project on this website that achieves the objective in <$50 (search for "start your car from a cell phone via GSM relay" on instructables)2. Following this idea you can even remote start your car if the need be!3. You can control up to 7 car functions (if the need be)4. You do not have to be a software wiz at all. You do need to be a hardware wiz either if all you need is to have one function (to do more look my addition in the comments)5. I don't see the author being too interactive / helpful. No blames just stating facts6. You may easily be able to start a lamp with this project but starting a car...see more »I see no point doing this project unless you have these parts lying around because you happen to be an Arduino and Electronics hobbyist. Here are the reasons:1. There is another project on this website that achieves the objective in <$50 (search for "start your car from a cell phone via GSM relay" on instructables)2. Following this idea you can even remote start your car if the need be!3. You can control up to 7 car functions (if the need be)4. You do not have to be a software wiz at all. You do need to be a hardware wiz either if all you need is to have one function (to do more look my addition in the comments)5. I don't see the author being too interactive / helpful. No blames just stating facts6. You may easily be able to start a lamp with this project but starting a car is a different ball game and certainly not intended here

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  • Make this Smart, Modular and Cheap Lithium Battery Charger System in minutes!!

    Let me get straight to the answers:1. I had to resort to the fixed supply dc-dc converter approach too after I noticed that any voltage lower than 20 v is not stable under high current conditions on the power supply model I purchased. 2. I noticed that 19.5V which is typically the output of a laptop power adaptor is not enough of a drive to deliver 4A charging current into a Li battery pack with 5 or more batteries. If you must use a laptop adaptor either make sure that your battery pack has 4 or less batteries or use a buck-boost converter (these are available readily too at the same price as a buck converter)3. I observed that dc-dc converters do sink current so I am now forced to change my earlier stance (in the comment that I deleted) on paralleling them. I no longer recommend paral...see more »Let me get straight to the answers:1. I had to resort to the fixed supply dc-dc converter approach too after I noticed that any voltage lower than 20 v is not stable under high current conditions on the power supply model I purchased. 2. I noticed that 19.5V which is typically the output of a laptop power adaptor is not enough of a drive to deliver 4A charging current into a Li battery pack with 5 or more batteries. If you must use a laptop adaptor either make sure that your battery pack has 4 or less batteries or use a buck-boost converter (these are available readily too at the same price as a buck converter)3. I observed that dc-dc converters do sink current so I am now forced to change my earlier stance (in the comment that I deleted) on paralleling them. I no longer recommend paralleling them since this may cause substantial damage.I do sometimes plan ahead and then wait endlessly to get the components from China. Sometimes by the time the components arrive, the design changes wasting time and money!

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  • Make this Smart, Modular and Cheap Lithium Battery Charger System in minutes!!

    Let mage get straight to the answers:1. I had to resort to the fixed supply- dc converter approach too after I noticed that any voltage lower than 20 v is not stable under high current conditions on the power supply model I purchased. 2. Go ahead and try and parallel up 2 buck converters. They should both be over current and short circuit protected. Just make sure to use diode isolation to avoid any of them sinking current. Set the exact same voltage to begin with. So just the usual protectiona really nothing out of the ordinary as long as they are both protected by design they should function well.I do sometimes plan ahead and then wait endlessly to get the components from China. Sometimes by the time the components arrive, the design changes wasting time and money!

    Lastly about the charging voltage: weigh the individual cells on a weighing scale. If the weight is 45g our more, feel free to go up to 4.15. V. If it weighs less than that do not exceed 4V.

    Hey...I had to resort to the fixed supply- dc converter approach too after I noticed that any voltage lower than 20 v is not stable under high current conditions on the power supply model I purchased. The under cabinet accent lighting 27a already designed the way you describe above so it was easy for me to switch to the design. Thanks!

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  • Make this Smart, Modular and Cheap Lithium Battery Charger System in minutes!!

    Yes it's 24V and that's enough fur your application.

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  • ranjeevm commented on MosfetN's instructable CleanBOT- Your DIY floor cleaning robot3 months ago
    CleanBOT- Your DIY floor cleaning robot

    Great job! But the steps lack specific instructions for someone to actually attempt to build this bot. A prime example is the missing software. Several other dimensions and specifications are missing ... so thanks but no thanks... to me this is an eyewash!

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  • ranjeevm commented on rexperry's instructable Convert a Vintage Light to Component LED3 months ago
    Convert a Vintage Light to Component LED

    LED technology is evolving by the day... if you ever have anything serious to do with them buy only the ready made bulbs from the most recognizable brands. I have LEDs mostly "Made in China - sold on eBay" kind of stuff (fitted by the previous owner) at my place that are about 1 year old. Purchased branded LEDs at Costco @$1.50 per bulb. There is no comparison in brightness, energy savings and overall life!! In my previous house I tried experimenting with DIY LED projects but thanks to the lack of quality control (on eBay and other popular websites) none lasted more than a few weeks. My projects have spanned COB and non-COB LEDs... COB LEDs are the ones used in this project... these are especially bad and none lasted for more than 3 days. I tried under rating them by reducing...see more »LED technology is evolving by the day... if you ever have anything serious to do with them buy only the ready made bulbs from the most recognizable brands. I have LEDs mostly "Made in China - sold on eBay" kind of stuff (fitted by the previous owner) at my place that are about 1 year old. Purchased branded LEDs at Costco @$1.50 per bulb. There is no comparison in brightness, energy savings and overall life!! In my previous house I tried experimenting with DIY LED projects but thanks to the lack of quality control (on eBay and other popular websites) none lasted more than a few weeks. My projects have spanned COB and non-COB LEDs... COB LEDs are the ones used in this project... these are especially bad and none lasted for more than 3 days. I tried under rating them by reducing the quiescent current to half that is rated but that wasn't encouraging either. Having warned you of the futility of this exercise, I hope that if you still do this project, you are luckier than I was!!

    Good information - I was browsing eBay with this info and see several LEDs of your description being sold. Questions - 1. The price seems to be around $1.50 so they are not too expensive. How long have these lasted in your projects? 2. Did you derate the current?

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  • ranjeevm commented on mukeshrudra's instructable SCROLLING DISPLAY 1FEET BY 6FEET6 months ago
    SCROLLING DISPLAY 1FEET BY 6FEET

    Without anything useful, this is less of an instructable and more of a show-off. For that purpose there is a platform called you tube!

    Without anything useful, this is less of an instructable and more of a show-off. For that purpose there is a platform called you-freakin-tube!

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  • Fast, Cheap and Modular Lithium Battery Charger System

    I think you are going a bit overboard without even reading the schematic. I am saying so because if you really paid attention you would see that the recommended power supply also has a built-in voltage control. This is actually more suitable for a test bench because it is a single component vs. your idea of two. I have so far not seen too much of merit in your comments and will spare myself from responding to them any more. Thank you!

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  • Fast, Cheap and Modular Lithium Battery Charger System

    If you recycle a laptop power supply, you can cut down the cost by $6 approximately because you still got to pay for the converter. If you would like a simplistic solution, everything including the DVM that you mention is optional more do if the batteries are self protected. Even for unprotected batteries, after the charger output is set to around 17v for a 4 pack, there is not much to protect from. My design is scalable in terms of type and number of batteries. I would still think that unless an effort is made to oversimplify In the interest of your hobby, there is no real need to knock off too many parts on this design.

    Unfortunately the current ones of my tool cabinet will add no value! I will keep updating this post as and when I have a better housing. I am planning to get a nice plastic one for around $10. For a start I thought that it was important to create and upload the blueprint for the comments and improvement ideas to start coming in.

    You are pretty much at a liberty to set a voltage of your choice but the data sheets of 18650 for samsung, Sony and a hand full of other manufacturers clearly indicate a max. saturation voltage of 4.25V. I don't think that using a DC converter is such a bad idea at all but it just sounds amateurish to me that I first convert 110V to 20V DC and then convert 20V to the exact charging voltage, The power pack I have suggested merely costs $10, can pump out 5A of juice at what ever voltage you need right up to 24V. So while I appreciate your comments, I wouldn't design the system based on your suggestion just to save $6.

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  • ranjeevm commented on gfwilliams's instructable Smart Battery Charger (no soldering!)6 months ago
    Smart Battery Charger (no soldering!)

    It is not really any cutting edge research any more but a well known fact. This info is available on the datasheets that every Ni Cd/MH battery manufacturer provides. Do not trickle charge those batteries unless it is a one off thing.

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  • ranjeevm commented on punkisnail's instructable Li-ion Battery Charger6 months ago
    Li-ion Battery Charger

    I just did in quite a bit of hurry...

    NP...We all are!

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  • ranjeevm commented on dagorald's instructable An improved moisture sensor6 months ago
    An improved moisture sensor

    Use a dremel to make a point sharper and ruggedize the top so that you are able to gently hammer the top. Just remember that hard soil can be loosened by watering over extended periods of time and no amount of ruggedization will help you if you are trying to put the sensor through rocks.

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  • ranjeevm commented on punkisnail's instructable Li-ion Battery Charger6 months ago
    Li-ion Battery Charger

    It is quite unnecessary to build your own charger this way. I recommend that you hook up a ready made switching power supply with a lithium protection circuit (for battery banks) with charging funneled through a thermostat. The voltage of the power supply would be 4.2 multipled by the number of batteries in the bank. The charging current should be about the same as the AH capacity of the battery. PS is $10, protection and thermostat are $3 each. For $16 you could construct a charger that is worth $85 or more in the market. If anyone needs help implementing this idea do let me know. If I get enough requests, I will post detailed instructions.

    I have never seen someone write 1V = 1A so let me be more explicit...what ****snail means that if a 1 ohm resistor has 1V across it, it is letting 1A through it.

    The age is of modular technology so unless you are an electronic hobbyist this project not for you. Even if you need a cheap / safe functional charger, this project is not for you especially if you do not have a pre-existing power supply of the right voltage. I am also not a big fan of making my own PCBs and usually get away using the general purpose ones when absolutely necessary. The only time I have made PCBs is when I am mass producing electronics. My quick suggestion would be therefore to buy a 2A switching supply ($8), a lithium protection module ($2) and a thermostat ($2) on ebay. You will then merely need to sequence them one after the other and bingo!... you just made myself an intelligent ultra fast charger that costs $75 in the market. Some of these circuits on eBay have fanc...see more »The age is of modular technology so unless you are an electronic hobbyist this project not for you. Even if you need a cheap / safe functional charger, this project is not for you especially if you do not have a pre-existing power supply of the right voltage. I am also not a big fan of making my own PCBs and usually get away using the general purpose ones when absolutely necessary. The only time I have made PCBs is when I am mass producing electronics. My quick suggestion would be therefore to buy a 2A switching supply ($8), a lithium protection module ($2) and a thermostat ($2) on ebay. You will then merely need to sequence them one after the other and bingo!... you just made myself an intelligent ultra fast charger that costs $75 in the market. Some of these circuits on eBay have fancy LCD display (of course at an extra cost) that will display the progress of charging. So go ahead and knock yourself out... P.S.: I am willing to post details if there are enough requests.

    When I do my calculations, your design seems to be outright dangerous to me. When the lithium battery is full discharged, it has a voltage is about 3.4-3.5 volts. With a 1 ohm current limiter, you will allow at least 4A current (since you are recommending a 12V power supply) to flow into the battery. For batteries that have a capacity lower then 1AH, this current will cause an explosion!!

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