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  1. Hi Siddharth, Also please mention from where you get LM-2936, because I could not get it here in Bangalore
  2. Hi Arun, In my house i have two sections of wiring, one runs all high power appliances like pump, refrigerator. Other line powers all low power devices like TV, FAN etc. I have connected my UPS to the second line. And I have told my mom to "NOT to use all of the appliances together" :) so we make sure that we don't overload the UPS. I have seen the UPS tranformer, its MOSFETs and I am fully aware of their limitations. In my first post i forget to mention that other than said modifications I have installed a 80mm FAN in the ups for cooling purposes. It takes care of cooling the transformer while charging as well as MOSFETs (and their heat sinks) when UPS is running as a backup supply.
  3. Yes, it does, as i mentioned in my post, my UPS is giving me a uninterrupted supply to my whole house for 3-4 hours. :) About transformer, you need to chanrge the external battery somehow right?, and your inbuilt charger can't carry it off, so you need to have separate charger. Instead of having a charger and UPS separately i Installed a charging
  4. In India also same DTMF signals are used. You can use a DTMF decoder IC to get BCD equivalent to the key pressed by the caller. When phone line is not used its voltage will be 50V DC, when it rings 50V AC will be applied by your exchange, when you pick up the phone its arround 12-16V across your phone.
  5. Ya.. even LED is also fine, but the reason why I switched to LCD is other than displaying speed in big fonts, i planed to show up odometer readings also in say 1minute intervals in small fonts. And using cellphone display is not possible because I need a font height of 1 inch, and 4-5 such characters. So display size is somewhere arround 1.5*3.5 inch. which is not there in old phones. Is it possible to get a character LCD display in 20x15 range.. :-\
  6. Hi, I have done the similar mod some three years back. What I have done is 1. I removed inbuilt battery, 7AH 12V sealed Lead Acid, in that place I installed a 5A 0-18V transformer and a battery change control circuit. 2. I installed a standard 120AH tubular battery outside ups. 3. Connected it to the board in the same place as that of the standard battery. 4. Removed the 1-2W wire resistor (which will be in the charging circuit) to isolate the inbuilt battery charging circuit. Its working fine for me since then, now i am using that 600VA ups for my home, with my mother watching TV when there is no power in the area for 4-5 hours. ;)
  7. Hi I am working on a digital Speedo project. I need to display speed reading in 3:1 digits (three digits and one decimal). Digits should be big enough to read from distance..(as Honda Civic has in its dashboard) I am thinking about using PIC16F628A for communication. But I am not sure about type of LCD I should use either a character based (like 20x7) where by joining lot of black dots i can make a digit, or a graphical display.. As per my logic even text displays can be used to display big digits, if multiple character blocks are used to display a single digit. Like the one in my example image. Only thing is digits will not be sharp, there will be some white lines in-between two dots. So alternative is to use a graphical LCD, but my concern is I never worked with graphical LCD, I am not sure whether 16F628 is enough for that or not So you need to suggest me now.. 1. What kind of LCD should i use graphical or character 2. PIC16F628 is enough or not Please note that I played only with this PIC till today in JAL, i never used a graphical LCD.. 3. Availability and cost of the LCD you suggested Please note that I am not bothered about temp. In India (that too in Bangalore) through out the year we have almost constant temp ;) attached is a sample display which i am looking for..
  8. The simple most circuit for this would be to take the circuit chip out of a dead watch or a table clock. They use a crystal oscillator and dividing technique. You need to cut off the coil winding and add two diodes (IN4148) on both the outputs (P side of it) and join the N-side to get study 1-Hz clock.
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