Sukhbinder

what is the difference between a high frequency and a transfomer based inverter. i read some where that transformer based systems have a load surge capacity of upto 200% but a high frequency system cannot exceed its surge capacity specified. i know that by using a high frequency allows the use of a smaller step up transformer but what about the excess electrical noise generated. can a high freq inverter drive all type of loads like fans, motor, TV sets. which one is the better choice?

Hi siddharth, seems u are a bit confused with the lm317 u need. u require an LM317T (the T prefix specifies that the device has a current rating of 1.5A). a normal LM317 has a rating of 1A. Since these devices are in the TO-220 package they can be easily heat sinked. but still u cannot get a cuurent output exceding 1.5A. use a bypass transistor as suggested for quite high cuurents u can use the old 2N3055 which comes in the TO-2 package ( like earlier power transistors) with a maximum current of 15A but a TO-220 package is also available but it handles lower currents. or u can use a TIP42 from texas which can handle currents upto 4A and is similar to the TO-220 Package. i suggest u use a PWM control as it is more efficient. use a Power Mosfet for PWM control (like IRF540). as for the turning problem, to make your turn to a side just stop the rear motor of that side and the car will swing on the rear wheel of that side using the wheel as a pivot, like if u need to turn left just stop the left rear wheel and the car will swing around using the rear left wheel as the pivot point.

i suggest u use the 7555 (the cmos equivalent of the 555). i happens that when a 555 switches states, it produces a surge of about 400mA which can easily upset the timimg for the other digital circuit elements, while a 7555 has a surge of just 10mA. i yself have been woking on this circuit and have got the components but due to lack of time i have not been able to finish it. i seem to have a circuit for a pulse stretcher in my notes, maybe this can help u out

Thanx ;)

Any thing that will work for both. I know about the working voltages for both TTL and CMOS but i still have to decide which type to use depending on their availability thanx ;)

H there all of u! i need a circuit to perform a power on reset for digital ics. i need something that is small ans simple using only simple discreet components like resistors,capacitors and transistor. no special ics please. the ic is a better choice but procuring it for me is a bit tricky here in INDIA. so i would really appreciate if u guys provided me with a simple solution. thanks ;)

Thanks

Any one having the datasheet for the TIL 31A phototransistor from texas instruments. thanks ;)

need a nokia 3650 and 6230i service manual ;)

why not try to power the digital clock from the power supply of the spindle motor. However the clock must be able to save the time just before it shuts off. u can try to use the signal at the spindle motor to trigger the counting of the digital clock (not the clock signal). generally most CD players use a permanent magnet DC micromotor for the spindle. computer CDROMs however use a stepper motor. the spin speed in CD players is usually controlled by using a PWM signal for the motor, so u would need filter (simple RC type would do it) before applying it to the clock. i suggest u use a diode in series to protect the clock circuit. if the player runs from 3V and the clock from 1.5v use 2 silicon diodes in series and the clock and player ground or negative must be common. as the CD player starts running the clock starts counting and as the CD battery goes dead the spin motor stops and the clock stops counting. u might need to invert the signal (use a simple common emmiter inverter as digital inverter ic's may not function well ,may be CMOS may work but it adds to the parts needed, so try keeping things simple). tell me if it works. ;)

Thanks for all your suggestions guys.

How do u measure the capacity with a discharge resistor and timer circuit. is it like this that u fix a discharge current value using a resistor and and find the time for which the cell can supply the current. u surely need high wattage resistors for it but what should the approximate range for the resisitor value be?

Thanks for the information but could u still provide me with a method to find the capacity of such type of cells. I need it to check out my cells. something that indicates its charge remaining and life remaing and condition.

hello kbe, i would like to kow that what kind of C-V measurements are u doing, i mean we have a C-V measurement unit in out lab but it measures the capacitance -voltage for MOS devices. u can use it for p-n junctions also. u also have the C-V measurements as the current voltage measurements. u can look up for instruments and techniques on the www.keithley.com, they make a number of measuring instruments and also have method to optimise and automated data acquisition.

Hi phil7, u can get quite a lot of information about ultasinic cleaners on google. the basic theory is that a piezo transducer is applied with a high frequency ( 30kHz-55kHz, that is why the word ultrasonics) signal. the piezo element vibrates with the applied frequency and these are coupled to the washing container. the oscillator output is usually applied to the peizo driver through a stepup transformer to obtain a high voltage drive. the piezo drivers are available commercially but keep in mind the encaplsulation of the system to prevent excessive noise and loss of effieciency. Use rubber washers to reduce the noise. Sukhbinder

thanks for the suggestions, if i don't get NiCd cells then i think NiMH cells will replace the NiCd cells well. i'll try to find the best fitting cells for it so that i can get maximum current also from them.

Try the character map utility in sytem tolls in windows with the symbol font. u'll get all the greek letter sybmols. just select one and click copy to copy to clipboard and paste it where u need it like this W. if u get a W written then just select it and change its font to Symbol. The Symbol font is a windows system font which is installed with the OS. ;)

Hi guys can any one tell me a way to find the current capacity for NiCd or NiMH cells. Usually its written on the cell itself but if u need to replace an internal customised cell , how do u do it. i have a black and decker 2.4V cordless screwdriver. the problem is that we donot have a black&decker authorised dealer or service centre in INDIA , i need to change its batteries but the capacity is not written on it any where, the size also is a non standard type like i think its a 1/2D. the cells are enclosed in a paper jacket and fitted in a plastic case. the screw driver is working fine till now but once the battery life goes down it may be difficult to predict its capacity. Does anyone have a generalised type circuit to find the mAh capacity for these batteries. ;)

thanks for ur help, i finally found that the transistor was a TIP42C, the number was covered with black ink. It uses a TOP222Y offline PWM switch in the power supply.i checked its datasheet which says its a 15-25W power device. can it provide enougt power to quick charge 4 2300mAh NiMH cells. i doubt these sony guys.

i'm having some problems with my sony NiMH charger. the charger has a TO-220 package transistor with the number 502 on it. i cannot find out if it is a BJT or a MOSFET. its a fairchild make i think but could not find anything on the fairchild website. can any one help me with this and get me its datasheet. the transistor is used to supply the current to the batteries and is connected to a LM358 IC. ;)

Glad to help u fenris. i have a USB MP3 player which is made in taiwan. it has a backlit LCD display which changes colour using a blue, red, and green leds. Mine has a built in lithium ion battery which can be charged from USB port of any computer or an iPod type travel charger. the later charges it in 1-2 hrs to full capacity. i get about 10 hrs from a single charge. I've hooked up mine to my car stereo using the headphone jack to the radio section as my sets tuner is not functional. it sure saves me lot on CDs and cassettes. no skipping and no dust problem, totally solid state. i think the manufacturers should look to this as a good new feature. Just carry ur music in a USB Flash drive, connect to the player and play. what more my mp3 player even suuports document files like any common USB drive for a computer. In addition to it it has a FM tuner with presets, voice recording via its inbuilt mic or from the FM. what else can u ak for. I've seen the single battery type MP3 players and i opened one to see a small DC-DC converter in it. the rechargable type are a bit expensive but u surely save in the long run. u may check out the site of sony who have launched new USB MP3 players with capacities of 512MB and 1GB. They by the name of SONY BEAN. the site says that u charge it for 3 min and get 3hrs of playback and 50 hr playback on a full charge.... Quite high end battery technology. By the way i have a 256MB and a 512MB player. ;)

Hi fenris, i would like to know that are u using a USB type MP3 player. Keep in mind that most such players donot have the audio output ground and power supply ground as the same. In such USB type of MP3 players the voltage from a 1.5 volt battery is stepped up by a DC/DC converter. If it has different colour selection for the screen then it is a step up type because u cannot drive a blue or green or even a red led from a 1.5v source. u may have to open up the player for finding the correct ground terminal. just chek for the continuity between the audio ground and the battery ground. if its not there u have a DC/DC converter based player

i need the layout for a UV currency checker or a lithography UV exposure unit. We require a UV exposure unit for exposing resist coated PCBS at our university. We had a mercury lamp earlier but it was too slow (took 1.5 hrs for correct exposure) we changed the lamp by the supplier gave us a sun lamp . It gives Visible as well as UV radiation but the heating is so much that the plastic mask gets heated up. Can some one help me outwith this for the specs for the tubes and the ballasts. ;)

Same was the case with me Ldanielrosa. i found two lithium coin cells in mine. There was coil in it but it was not connected and for the magnet they just put in a metal stud. these cheats... they sure dupe the customers well. >:(

sorry guys the working time is 5 mins as per this site but i remember seeing 15 min at some other site. u need to shake it for 15-30 sec and u get a working time of 5 mins.:D