hello everyone this is my first time being here at EP and am glad i found this place. I am having some problems getting my TIP-127 PNP to work properly. here is some background info on what i am trying to do.
Pic16f88 programmed with 3 outputs each of these 3 outputs go to the Base pin on the TIP-127. One of these outputs Will be a PWM output.
My logic for switching the TIP127 on is correct in the software (Logic 0 turns Tip on)
if i measure the output pin of the PIC outputs are acting proper to what i have programmed.
I plan on driving 3 solenoids at 22ohms@12v here is my calculations
using ohms law i calculate .545 amps draw at solenoid.
Minimum base current=545ma/1000hfe=.545ma+a lil to ensure full saturation so .700 sounds good?
Rbase=12/(.545/1000*.7)
Rbase=32K ohms
Power dissappated= .3(.545)=163mw
my problem is when i have a high condition on the output pin,my TIP is at 12v on the collector(no load-just measured with a volt meter) When the output pin is brought low the TIP is still at 12v.
This is the first time i have worked with a TIP transistor and am clearly doing somthing wrong. can anyone help me understand whats going on here. ill check back often if anyone has further questions.
Thanks
Jason
Pic16f88 programmed with 3 outputs each of these 3 outputs go to the Base pin on the TIP-127. One of these outputs Will be a PWM output.
My logic for switching the TIP127 on is correct in the software (Logic 0 turns Tip on)
if i measure the output pin of the PIC outputs are acting proper to what i have programmed.
I plan on driving 3 solenoids at 22ohms@12v here is my calculations
using ohms law i calculate .545 amps draw at solenoid.
Minimum base current=545ma/1000hfe=.545ma+a lil to ensure full saturation so .700 sounds good?
Rbase=12/(.545/1000*.7)
Rbase=32K ohms
Power dissappated= .3(.545)=163mw
my problem is when i have a high condition on the output pin,my TIP is at 12v on the collector(no load-just measured with a volt meter) When the output pin is brought low the TIP is still at 12v.
This is the first time i have worked with a TIP transistor and am clearly doing somthing wrong. can anyone help me understand whats going on here. ill check back often if anyone has further questions.
Thanks
Jason
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