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Thu, 04 Dec 2008 15:20:42 -0800 http://backend.userland.com/rss092 HI everyone, i am developping an application called " shorting mechine control " using 89c51.the key idea of this project is con <noauthor@nospam.com> http://www.8051projects.net/forum-t10341.html Try the following logic:1. enable the external interrupt int0 and timer1 as a 16 bit timer.during the initialisation of the timer1, see that the TR1 b pdi33<islurpundalik@nospam.com> http://www.8051projects.net/forum-t10341.html hi @ pdi33, i am controlling 16 valves all together ,so i cant use interrupt logic here as all 32 io pins are used (16 for valves and 16 for input sig caze<rajeev.caze@nospam.com> http://www.8051projects.net/forum-t10341.html Hello caze,if you plan to do it in PWM, heres how it can be done : change the output transistor according to your load. its always good to use optocou Arun Kumar V<nura1002003@nospam.com> http://www.8051projects.net/forum-t10341.html hi caze,o.k. now i understood the PWM requirement from ur second post. If ur micro is not being used for any other purpose, then u can simply poll con pdi33<islurpundalik@nospam.com> http://www.8051projects.net/forum-t10341.html hi, after a long search , i ve got IRFD014 power transistor , which has drain current of ID= 1.7 AMP. can i use it . caze<rajeev.caze@nospam.com> http://www.8051projects.net/forum-t10341.html just confirm whether ur logic is as shown in the figure below pdi33<islurpundalik@nospam.com> http://www.8051projects.net/forum-t10341.html hi @ pdi33,thanks for the reply. this is exactly what your last post (figure) says.i have written an assembly program (its prototype)to execute my pro caze<rajeev.caze@nospam.com> http://www.8051projects.net/forum-t10341.html hi @ Arun , thanks for the help.this is exactly what i wanted.how to choose the value of R1 and R2 , and how about the transister bc caze<rajeev.caze@nospam.com> http://www.8051projects.net/forum-t10341.html Hello pdi33,But the silver lining is that u require only three states at ur output i.e. 0%,100% and 40% so i think it is just possible.... if i am not Arun Kumar V<nura1002003@nospam.com> http://www.8051projects.net/forum-t10341.html hi, one more query.. do i need to connect a capacitor between groung and vcc of microcontroller.and between ground and power supply of PCB. i caze<rajeev.caze@nospam.com> http://www.8051projects.net/forum-t10341.html hi @ arun, the valve which i am using is of 35 watt,1.43 amp. can i use BC 337 for the same. and how about my program which i have posted caze<rajeev.caze@nospam.com> http://www.8051projects.net/forum-t10341.html caze,1.43A is too high a current for a small transistor like BC337. For that high a current u may have to use a power transistor like 2n3055 or mosfe pdi33<islurpundalik@nospam.com> http://www.8051projects.net/forum-t10341.html hello caze, No, you can't use a 800mA transi for a 1.5 amp job, it'll fry ! try a mosfet or a power transi like BDX seriesArun Arun Kumar V<nura1002003@nospam.com> http://www.8051projects.net/forum-t10341.html Hi Caze,as a general rule of thumb, you have to use a device which can handle 3-4 times your actual load. your load is 1.4 amp and your switching devi Arun Kumar V<nura1002003@nospam.com> http://www.8051projects.net/forum-t10341.html hi , arun, but the current rating of these devices are too high.its 28 amp for irf540 and 50 amp for irfz44. will it not burn the valve...a caze<rajeev.caze@nospam.com> http://www.8051projects.net/forum-t10341.html HI @ Arun, the very first post which u have posted me regarding optocoupler , In that the load is connected to the emiter. what if caze<rajeev.caze@nospam.com> http://www.8051projects.net/forum-t10341.html Hi Caze,you can connect it that way, and you need R only in case of mosfet and not transistorit can be of 100k-1meg value. for R2 you can use 10k. but Arun Kumar V<nura1002003@nospam.com> http://www.8051projects.net/forum-t10341.html Caze,it's typical of inductive loads to draw a pull-in current of ~10 to 20 times the hold current.So the mosfet suggested by Arun is just apt.With in sashijoseph<sashijoseph@nospam.com> http://www.8051projects.net/forum-t10341.html hi sashijoseph, would u please be more clear for your last post .i m unable to make sense of the last sentanse. and also ""apt.""" caze<rajeev.caze@nospam.com> http://www.8051projects.net/forum-t10341.html hi @ arun, my silly question was not that i mean what i wantd to know is .."" Is there any procedure/rule/formula to deter caze<rajeev.caze@nospam.com> http://www.8051projects.net/forum-t10341.html hi @ arun , i am so sorry for my last post.. i would't have post like that ..its was really a stupid thing done by me ..m so sory for that.... caze<rajeev.caze@nospam.com> http://www.8051projects.net/forum-t10341.html hi caze,you don't have to be too formal, i was just trying to emphasize that some times these things are not mentioned in any text books and you have Arun Kumar V<nura1002003@nospam.com> http://www.8051projects.net/forum-t10341.html hi everyone , my project is finished and its in final stage . thanks to everyone for their help and time... caze<rajeev.caze@nospam.com> http://www.8051projects.net/forum-t10341.html Hello Caze, Congrats on completion of your project ! Arun Arun Kumar V<nura1002003@nospam.com> http://www.8051projects.net/forum-t10341.html Congrats caze Do not forget to publish it here on 8051projects.net Ajay<contact@nospam.com> http://www.8051projects.net/forum-t10341.html