Questions tagged [open-collector]

An open collector is a common type of output found on many integrated circuits (IC).Instead of outputting a signal of a specific voltage or current, the output signal is applied to the base of an internal NPN transistor whose collector is externalized (open) on a pin of the IC. The emitter of the transistor is connected internally to the ground pin. If the output device is a MOSFET the output is called open drain and it functions in a similar way.

Filter by
Sorted by
Tagged with
16
votes
1answer
15k views

Open Drain vs Open Collector

Is there a practical difference between Open Drain and Open Collector outputs, or are the terms used interchangably? If they are indeed different, what are the contexts where each is advantageous? My ...
10
votes
1answer
390 views

Connect two different sources with two Digital Ouptuts using an Adam 4055

I would like to operate an Adam 4055 module to control two different applications having their own power supply. Adam 4055 is Digital Input/Output control module over RS-485, I use only the DO part ...
7
votes
1answer
879 views

Open collectors & 74LVC245

I am trying to interface a PS/2 keyboard to a MSP430 for a toy. The PS/2 keyboard runs off 5V, but the MSP430 microcontroller runs off 3.3V. So I have a 74LVC245 level shifter to convert between the ...
6
votes
4answers
9k views

Why do they usually make comparators open collector?

I never see open collector opamps while I frequently see open collector comparators. What is reason for preferring open collector output in comparators? (Inside of LM193.)
6
votes
1answer
539 views

How does the Nintendo 64 detect a controller is connected?

To give some context, I am trying to emulate controller input to the N64 via a GPIO pin on the Raspberry PI. In an attempt to accomplish this, I have one of the PI's GPIO's in a pull-up configuration ...
5
votes
6answers
1k views

Difference between no input and a zero input in digital electronics

I'm new to digital electronics and try to understand how logic gates works. In books many times Zeroes​ and ones are referred as Low and High respectively, is Low and High used as an indication of ...
5
votes
4answers
1k views

Why are the outputs of these gates tied together in the Apollo Guidance Computer?

In looking at the AGC schematics, I'm finding a lot of instances where the outputs of some of the NOR gates are tied together when feeding into another gate. The most dramatic example being here, ...
5
votes
2answers
7k views

SPI and pullups. Is it ever used in open collector configuration

Is SPI ever wired as open collector in devices calling for the use of pullup resistors? Everything seems to point to it usually being totem pole but I wonder if there are exceptions. The only pullup ...
5
votes
6answers
3k views

Why do I2C lines use open drain driver instead of tri-state drivers?

My understanding is that I2C lines use pull-up resistors to passively pull up the bus to logic high because the drivers used on the bus are active drivers, namely open collector/open-drain. Since open ...
4
votes
1answer
10k views

What's the difference between a 74LS05 hex inverter and a 74LS04 hex inverter?

It looks like the 74LS05 has "open collector outputs" (not sure what that is) and the 04 does not. Plus, it appears the ...
4
votes
4answers
3k views

Using an open-collector output from one IC to trigger a level change on the input pin of another IC?

So my problem is simple: I have an IC that provides an output pin to alert you when some condition is met. The output pin is open-collector, high-impedance when active. I want to monitor this output ...
4
votes
2answers
6k views

Simulate tach signal of PWM fan

I have a power supply that uses a PWM fan with 4 wires. Wires: 12V (red), GND (black), PWM Control (brown), TACH Sig (white) The fan speed is controlled by the PWM control wire (brown). Fan speed is ...
4
votes
1answer
199 views

Identify this open collector serial protcol

I'm trying to analyze the serial link between two devices, respectively a motor controller board and a Li-Po battery manager, which battery powers both devices. The application is a battery-powered ...
4
votes
4answers
2k views

Open collector microcontroller output

I am building the following circuit, in order to control the P channel MOSFET as a high side switch for my load. The input of this circuit will be from a microcontroller (maybe an STM32F103), and I ...
3
votes
1answer
2k views

May I connect two open collector outputs in parallel

May I connect two open collectors like this in parallel? simulate this circuit – Schematic created using CircuitLab
3
votes
4answers
2k views

Purpose of pullup resistor in BJT LED driver circuit

One answer to this question suggests the following circuit to drive a LED from an open collector output of a 74LS47: simulate this circuit – Schematic created using CircuitLab What is the ...
3
votes
4answers
761 views

What is an open collector?

I am new to electronics, and I'm reading a book on embedded systems and bumped into an "Open Collector". I know that a transistor has a base, which acts like a switch for the current to flow from ...
3
votes
3answers
1k views

Interfacing open-collector optoisolator to 3.3V microcontroller

I have a bit of a puzzle on my hands trying to interface a Fairchild MID400 optoisolator (popular "logic level" optoisolator for mains detection) to a 3.3V GPIO pin. The MID400 is a 5V part [*] and ...
3
votes
2answers
240 views

When using an open-drain output to drive an NPN transistor, can the base resistor be replaced by a pull-up?

Assuming the value of R1 is the correct value for the base resistor for the given motor L1, is it okay to omit the additional base resistor, used in push-pull applications, for an open-collector ...
2
votes
3answers
773 views

Is controlling a voltage regulator's EN/SHDN terminal directly by 3.3V microcontroller possible?

Let's take the LT1763. The datasheet says that "The SHDN pin can be driven either by 5V logic or open-collector logic with a pull-up resistor." On the other hand the chart "SHDN Pin Threshold Off-to-...
2
votes
2answers
9k views

difference between dry contact mode output and open collector output

We have a device which can work with dry contact input and a device which gives open collector output. Will it inter-operate? Is there any difference between dry contact mode output and open ...
2
votes
2answers
409 views

Question regarding 7402 IC

I want to create a SR latch using 7402 IC. I would like to read the output (i.e. Q value) from the IC using an ADAM-6066 which has the following specs for digital input: Wet contacts: Logic level 0: ...
2
votes
2answers
1k views

PIC18F2550 I2C Open Drain?

As far as I have read, the I2C pins are Open Drain or Open collector, but in the PIC18F2550 the datasheet doesnt say anything about those pins, and even says they are a digital output if you select ...
2
votes
3answers
2k views

Open Collector/Drain vs Push pull

Given the situation where an LED is being used for a status indicator or similar, not toggling quickly. Which is the best configuration for the IO pin, push pull or open drain? As I see it either ...
2
votes
1answer
3k views

Interfacing PS/2 Keyboard to 3.3V inputs

I have had wonderful success with my new Mojo FPGA, so I decided to try something more difficult, interfacing with a PS/2 keyboard, but I cannot get it to work. Of course, I took the proper ...
2
votes
1answer
1k views

Do you have to set the TRIS register when using open collector outputs on Microchip microcontrollers?

I'm using a dsPIC33FJ series microcontroller from Microchip. It has dedicated open-collector outputs/registers. I've read the documentation and it is extremely brief. Does setting the ODCx register ...
2
votes
2answers
559 views

Open Collector Comparator for Voltage Glitch Detection

I recently ran a round of PCBs which included an experimental circuit to detect short glitches in my input voltages. I attached the schematic for reference: The intent is that C29, in parallel with ...
2
votes
1answer
61 views

Help on translating 5V rotary signal output to interface with lathe's cnc controller!

I have a hall sensor (OH137 - open collector) as an index signal on my lathe’s spindle. I have the sensor pulled high by a 1k resistor and can’t change it because they’re both glued in epoxy. This ...
2
votes
2answers
469 views

Open collector with Atmega48

After looking at this, I think I already know the answer, but I just wanted some clarification. Open collector microcontroller output I have a part that is going to drive my mosfet at 15V. I have ...
2
votes
1answer
1k views

Controlling 2 relays with 1 Open-Collector output

I had a board with open/collector output pins, and i need to control 2 relays syncronioulsy (open and close at the same time) with 1 open collector output. So how can make the connectıon from pin to ...
2
votes
1answer
239 views

How to control bi-directional logic line bypassing the open-collector stage?

The uBlox Leon G100 GSM modem has a bi-directional RESET_N line (active-low) that controls the reset of the modem but also indicates whether the modem is up or down (modem out MCU in). Because the ...
1
vote
3answers
2k views

Open Drain Serial TX output on Arduino

I have been trying to implement an open drain Serial output using a Arduino Nano. In the following example I have used 2 Arduino Nanos (both operating at 5V Vcc), using one Arduino as the transmitter ...
1
vote
4answers
2k views

Input pins hardware interface uC

I am trying to figure out how to interface a A2235-H GPS module. The datasheet says that one pin(nRST) must be connected to open collector or open drain output of uC while an other one(ON_OFF) must ...
1
vote
4answers
3k views

Wired-or open drain with open collector outputs

I have a comparator with open collector output (LM311) and a gate with open drain output (SN74LVC1G06). I want join these two outputs to make a wired-or, with a pull-up resistor tied to +3.3V. In a ...
1
vote
2answers
3k views

Adding Low Pass Filter to Open Collector Hall Sensor

I'm using a gear tooth sensor to create pulses when a metal object passes the sensor. There's a lot of noise on the signal so I decided a simple low pass filter would suffice(f-cutoff = appx.400hz). ...
1
vote
3answers
1k views

Using Raspberry Pi to read open collector outputs from tally connector

Please forgive my ignorance, I'm a software programmer who is new to the electrical and hardware side. Our Panasonic HS300G video switcher has a Tally connector. Below is the pin diagram and circuit ...
1
vote
2answers
2k views

Why does the I2C interface use the open-collector/open-drain?

The open-collector adds inconveniences like requiring an external pull-up resistor and slows down the throughput. Why did the I2C designers choose to use open-collector/open-drain?
1
vote
1answer
850 views

Why is there no open-collector OR-gate in the 7400 series? [closed]

I searched in the "List of 7400 series integrated circuits" on Wikipedia for a open-collector OR-gate, but couldn't find any. The list looks complete, so I assume there is no such chip in the 7400 ...
1
vote
1answer
781 views

Voltage protection of PNP Open-Collector Pull-Down Resistor Circuit

Circuit Consider the following U-Shaped Micro Photoelectric Sensor Panasonic PM-T54P with two PNP Open-Collector Transistor outputs: I chose the supply voltage to be 12V DC. In the place of the two ...
1
vote
1answer
61 views

Define the purpose of these components in the operation of this low side driver

I am trying to understand the operation of the following low side driver circuit I found in a schematic of an old pinball machine (redrawn for clarity): L1 is a Solenoid and Q1 is a Darlington BJT (...
1
vote
1answer
124 views

What is the purpose of this schottky diode reversed across the BJT base resistor?

In a design for the popular "gotek" floppy drive emulator, as per the standard, the outputs from the floppy emulator are open-collector. An STM32 is used as the processor. This drives a 74HC04, which ...
1
vote
2answers
2k views

How can I interface a Raspberry PI GPIO to an open collector circuit to send / receive data?

I have a GPIO from a Raspberry PI connected to a Nintendo 64 system like so: From what I've gathered and observed, the data line on the N64 system is an open-collector output. The line is tied high ...
1
vote
2answers
1k views

Using open collector as regular 5v output

I'm trying to use the following IC: SN74S289BJ so that the output is 5v when HIGH and ~0v when LOW, however I'm having problems due to the open collector nature of it, as I've written data to a ...
1
vote
1answer
96 views

Open collector / drain question

I'm trying to to find the best way to force an inverting amplifier to postive saturation with a gate input, but otherwise leave the function of the op-amp intact. I've come up with a few ways to do ...
1
vote
2answers
291 views

ULN 2003 open collector

I have searched for troubleshooting the ULN and did not find any solution. I use a ULN chip in a motor inverter for controlling precharge relay and main relay. The problem is when the motor inverter ...
1
vote
1answer
91 views

How to handle Digital Input Interface

Below in right side there is an discrete output signal circuit implementation and as a platform i need to read this signal somehow. I have a discrete input interface. My question is how can use my ...
1
vote
2answers
311 views

Arduino + LS7407N to shift logic levels in serial communication

I'm trying to drive a device that uses 12-0V levels for serial communication. I decided to use LS7407N, a buffer with open-collector, so that I can use Arduino's TTL levels to send commands to the ...
1
vote
1answer
106 views

Purpose of base-collector resistor in open-collector opto-isolated GPIO output

I've been working with an opto-isolated output for a high-speed camera I'm interfacing with and was a little puzzled by the circuit they were using for an opto-isolated open collector output. As far ...
1
vote
0answers
67 views

Open Collector Output connection to a relay

Hey sorry if this question is too simple, as i am not an expert in this. I have a device ( industrial router, works at 0- 30vdc) which has a Galvanically isolated Open collector ( External 0-30 VDC, 0....
1
vote
1answer
55 views

Does the 74LS09 have an adequate internal input pullup?

I want to feed an output of the 74LS05 open collector inverter into one of the inputs of the 74LS09 AND gate. The internal schematics in the datasheet shows that there is an internal resistor and 2 ...