Electronics, PCB Design and PCB Layout Daycounter, Inc.
Engineering Services

Custom Firmware, Electronics Design, and PCB Layout

    Home Company Services Products Partners Clients Site Map Contact Us
                 
 

Capabilities

Electronics Design
Firmware Development
Software Development
Embedded Design
PCB Layout
Digital Signal Processing (DSP)
Reverse Engineering
Prototyping
Device Driver Development
VHDL
Motor Controllers
Microcontrollers
Data Acquisition Systems
Palm OS Software
Windows CE Software
Pocket PC Software
Design for Manufacturing
Through Hole to Surface Mount (SMT) Conversion 
Microchip PIC Consultant
MSP430 Development
DSP56 Development
RoHs Redesign
Design for USB

 

Latching Momentary Switch Circuit

See our other Circuits.

Momentary switches turn on only when pushed. Latching switches require a press turn turn on continuously and will toggle off with a second press. Latching switches are more complex mechanically, larger, and more expensive.  The circuit below creates latching action from a momentary switch. 

When the circuit is powered up, all of the transistors are off and stay off. C1 gets pulled up to Vp.  When the switch is pushed, Q3 and Q2 turn on, since their base is pulled up. Q1 and Q4 are in turned on as well.  Q1 keeps Q2 turned on and Q2 keeps Q3 turned on and Q3 keeps Q4 turned on.  Q4 supplies current to the load. When Q2 is asserted it keeps pin 1 of SW1 at ground. 

When the switch is pulled low again, the base of Q3 is tied to ground, because Q2 is on, and the chain is broken an all of the transistors turn off. 

C1 and R1 and R5 form the time constant for the debounce circuit.  Adjust these values for an appropriate debounce time. 

Do you need help with an electronics design?  Daycounter provides contract electronics design services. Contact us to give you a quote on your electronics design project.

 

[Employment] [Downloads][Articles] [Contact Us]

Call us now at 1.801.938.4264

Copyright 2004 Daycounter, Inc.  All rights Reserved.






Soil Moisture Sensor Probe



Water Level Sensor