TTL input circuit to drive diode

Started by Gary H in sci.electronics.basics11 years ago 5 replies

Hi. I need a little help with something that should be pretty basic. I have a control board that has a TTL output to turn on and off a laser. ...

Hi. I need a little help with something that should be pretty basic. I have a control board that has a TTL output to turn on and off a laser. The laser is nothing more than a diode that consumes about 60mA. So, I want to be able to turn the diode on or off with the TTL output. I don't really know much about TTL requirements. But, would a NPN transistor with resistor between the bas...


mosfet? transistor? hexfet?

Started by Anonymous in sci.electronics.basics11 years ago 11 replies

When would one use a transistor? mosfet? hexfet? Basically looking into PWM switching of medium-sized DC motors (12V, ~5A or so). Which...

When would one use a transistor? mosfet? hexfet? Basically looking into PWM switching of medium-sized DC motors (12V, ~5A or so). Which should I use...? A beefy transistor like a TIP36C? Or a hexfet like IRLZ34NPBF (98c at Mouser)? Thanks... Michael


lm 350 problem

Started by lerameur in sci.electronics.basics11 years ago 3 replies

hello, I wanted to know if by using two lm350 in parallel, I would be able to use 2 * 3amp ? One of them usually regulated a max of 3 amp. I...

hello, I wanted to know if by using two lm350 in parallel, I would be able to use 2 * 3amp ? One of them usually regulated a max of 3 amp. I also, I heard i could add a transistor in parallel to one LM, where would be the base and collector hooked to , assuming (NPN) the emitter is at the output. thanks ken


How to count pulses per second ?

Started by Mike C in sci.electronics.basics11 years ago 79 replies

Hi, I'm hoping someone could help me create a very basic circuit which would: Count the number of pulses it receives per second (from a 555...

Hi, I'm hoping someone could help me create a very basic circuit which would: Count the number of pulses it receives per second (from a 555 timer, or a switch, for example) and if the number of pulses per second is equal to, or greater than 10 it turns on a transistor. So basically it should check every second if a clock frequency of 10Hz is being met - if so, a transistor should turn an...


Re: Low on-resistance bipolar transistor - does it exist?

Started by John Popelish in sci.electronics.basics11 years ago 9 replies

tempus fugit wrote: > Hey all; > > A transistor thread in this group got me wondering about transistor > characteristics. I have seen low...

tempus fugit wrote: > Hey all; > > A transistor thread in this group got me wondering about transistor > characteristics. I have seen low (and very low) on resistance MOSFETS (2 > ohms and less) but haven't seen a similar spec in a standard BJT. In fact, > sifting through the Fairchild site, one can sort the MOSFETS based on Ron, > but the same isn't true for the BJTs. Are some BJTs lower


transistor 2n3055

Started by Bob Clark in sci.electronics.basics10 years ago 34 replies

The transistor 2N3055 is packaged in a TO3 case. It has its collector "grounded" to the case, and the base and emitter to the two pins. ...

The transistor 2N3055 is packaged in a TO3 case. It has its collector "grounded" to the case, and the base and emitter to the two pins. NPN transistors are usually used with the emitter going directly to ground, and the collector somewhere far from ground. Can someone give me a typical application for this 2n3055 transistor, showing how it is typically used in a circuit? What am I missing...


sizing a freewheeling diode for a coil

Started by Matt in sci.electronics.basics10 years ago 38 replies

I am controlling the coil of a relay using a switching transistor. To protect the transistor I intend to use a freewheeling diode in parallel...

I am controlling the coil of a relay using a switching transistor. To protect the transistor I intend to use a freewheeling diode in parallel with the coil. I'm not sure of the issues in specifying the diode. My impulse is to simply use a 1N4007 http://www.fairchildsemi.com/pf/1N/1N4007.html (1000V peak repetitive reverse voltage, 1.0A average rectified forward current) because it is ...


How to use MOSFETs ?

Started by Jan Nielsen in sci.electronics.basics10 years ago 5 replies

Hi, I was told on another forum, that the way to switch "large" currents is a MOSFET since a regular transistor cant, atleast not from a mcu...

Hi, I was told on another forum, that the way to switch "large" currents is a MOSFET since a regular transistor cant, atleast not from a mcu output. Now I have a few of these IRF530 MOSFETs, and are trying to get them working. I connect ground/common to one of the outer legs, a led (cathode) to the other outer leg. The anode of the led to VDC+ (4V) Then I connect the base to a 1K ...


Q: Transistor as a switch with pull down ?

Started by in sci.electronics.basics10 years ago 13 replies

Hi all. I am interfacing an PIC microchip to a relay by using a normal NPN transistor. The relay is connected between +12v and collector....

Hi all. I am interfacing an PIC microchip to a relay by using a normal NPN transistor. The relay is connected between +12v and collector. A protection diode in reverse has also added. Emitter is grounded. My concerne is that by only adding a 10k resistor between base and the digital output pin (5v) the base will be floating if the PIC failes to start as all IO pins are default input. Would...


Zener questions

Started by Allen Bong in sci.electronics.basics10 years ago 40 replies

I have 2 questions regarding zener wattage. 1. Can I parallel two 1W zener to get a 2W zener ? 2. Can I increase the wattage of a zener...

I have 2 questions regarding zener wattage. 1. Can I parallel two 1W zener to get a 2W zener ? 2. Can I increase the wattage of a zener using a bipolar transistor arranged as below? Rload Vin ___ Vout o---------|___|-------------o-------------------o | ...


lab power supply

Started by duns...@gmail.com in sci.electronics.basics10 years ago 13 replies

hi to all i'm an italian electronics hobbyist, i'm sorry for my bad english :( in this holiday i try to build my first lab fully adjustable...

hi to all i'm an italian electronics hobbyist, i'm sorry for my bad english :( in this holiday i try to build my first lab fully adjustable power supply unit i try to hack the scheme at pag.8 of the datasheet of the lm317 http://www.ortodoxism.ro/datasheets/nationalsemiconductor/DS009063.PDF for add the negative section, the tracking voltage mode, the transistor for increase the output cu...


Capacitor charging curve

Started by Sambo in sci.electronics.basics10 years ago 12 replies

I am planing to put together PIC project to measure SMD caps. I am not sure if the answer will help me for this project and how I started...

I am planing to put together PIC project to measure SMD caps. I am not sure if the answer will help me for this project and how I started wondering about it but it has been bugging me for a while ( if I was hoping to discharge through a transistor leaving .7V on it ? during repeating measurements. or was it discharging to some voltage so it coincides with the voltage reference point. ...


Need for inductive kickback diode

Started by Martin in sci.electronics.basics10 years ago 11 replies

If you are using PWM to control the brightness of an incandescent light, should you use an inductive kickback diode to protect...

If you are using PWM to control the brightness of an incandescent light, should you use an inductive kickback diode to protect the transistor? It is of course recommended to use when you are driving coils, relays, motors, etc. A light is a coil, althought I would guess the inductance is pretty low. Would good practice be to put the diode in "just in case", or its absolutely unneeded?...


Driving a PNP Darlington transistor from a PIC16F877A

Started by scouselad in sci.electronics.basics10 years ago 5 replies

Hi, I'm designing an electronically-controlled light dimmer circuit based on one I found at: http://www.edn.com/article/CA46649.html I'm...

Hi, I'm designing an electronically-controlled light dimmer circuit based on one I found at: http://www.edn.com/article/CA46649.html I'm replacing the SG3524 PWM chip with a PIC16F877A and I intend to take a digital input from the user and (scale it, then) compare it with the 0-5V from the op-amp (digitised using the PIC's ADC). As you can see from the diagram, the PWM signal drives a PNP ...


Simple transistor NOT gate

Started by Allen Bong in sci.electronics.basics10 years ago 18 replies

Hi, Is it possible to construct a simple inverter gate using 1 or 2 transistors and resistors? I tried the circuit below but it doesn't...

Hi, Is it possible to construct a simple inverter gate using 1 or 2 transistors and resistors? I tried the circuit below but it doesn't work at all. VCC + | | .-. | | | |4K...


2 Transistor AM Radio

Started by Dave.H in sci.electronics.basics10 years ago 19 replies

Not sure if this is the correct place to ask, but here goes... I've found plans for a simple two transistor AM radio receiver, but I'm not sure...

Not sure if this is the correct place to ask, but here goes... I've found plans for a simple two transistor AM radio receiver, but I'm not sure how the ferrite loop antenna is connected to the radio. I'm not at all good with schematics, I can understand most of it except for the ferrite antenna bit. I would appreciate any help on this. http://www.techlib.com/electronics/crystal.html#Simp...


TO-220 pinout standard?

Started by Anonymous in sci.electronics.basics9 years ago 11 replies

Is it standard that a TO-220 transistor package is, with the tab up, with the markings facing you, Base, Collector, Emitter? (for example, on...

Is it standard that a TO-220 transistor package is, with the tab up, with the markings facing you, Base, Collector, Emitter? (for example, on the TIP31A) I noticed the TO-92 2N3904 I have is (with the markings facing me) E B C, and a TO-92 2N2222 data sheet even shows C B E !!! Michael


Don't touch that base lead! (Photo Transistor)

Started by jalb...@bsu.edu in sci.electronics.basics9 years ago 8 replies

I want to play around with some phototransistors and am curious about the base lead. It seems like this lead is treated as taboo . ...

I want to play around with some phototransistors and am curious about the base lead. It seems like this lead is treated as taboo . Some sources say it's just there but you won't have to or don't need to use it. Other sources say that it is there so that you can bias the transistor but don't go any further. What effect does applying a bias current have on the function of the phototransis...


Question about transistor breakdown voltage

Started by Anonymous in sci.electronics.basics9 years ago 21 replies

I see in the specification sheet for a darlington transistor that its collector to emitter breakdown voltage is 100V. What is its emitter to...

I see in the specification sheet for a darlington transistor that its collector to emitter breakdown voltage is 100V. What is its emitter to collector breakdown voltage? The same? Thank you in advance. Gerb


What range should my POT be?

Started by kayvee in sci.electronics.basics9 years ago 23 replies

Okay, so I have this motor and it is powered by a 24VDC power supply, and I would like to vary the voltage going to this motor. This motor draws...

Okay, so I have this motor and it is powered by a 24VDC power supply, and I would like to vary the voltage going to this motor. This motor draws 0.4A with 24V. I understand that connecting a pot normally to this motor will burn out the pot rather quickly, so one must use a NPN transistor. I reckon in this fashion: V+ ---+---------------+ | | P /c ...