latch for a diary?

I have a comp notebook as a diary and a key lock, but how can I make a latch to put the lock on the diary? thank you! I will try to look at your answers ASAP! TN777

Question by TN777   |  last reply

electric release latch

Hi! I'm trying to figure out how to go about creating a latch where applying an electrical current would release it. Probably something involving an electromagnet. I apologize (1) for the sudden flurry of board posts, and (2) if this is not the best board for this specific question - I know it's not exceptionally techy, but it looked like the best option. Thanks!!!!!!!!!

Topic by Purple Chez   |  last reply

Hidden Door Latch

I am looking for a secret "latch" to open/close a bookcase that covers a hidden door. There are some nice electromagnet types but they are expensive and need power. Any ideas on a "Chinese puzzle" type of thing where you move a couple of things and it opens? I don't want the classic horror movie things like move a book, lever or statue 'cause that's the first thing someone would try. Just fishing for ideas!

Topic by Greenehouse   |  last reply

Latching Laser Alarm?

I'm here again guys to ask you this question, will this circuit work? More Importantly, is the LDR placed correctly? 'cauz I'm having doubts on this circuit :S  And I'm going to make a PCB for it, and I'm too lazy to test it on a bread board (too lazy to solder wires on parts with big pins, e.g. DC Jack). If this circuit will not work I'm going to switch to relay laser alarm types. Just give me the answer please. Thanks :D 

Question by Charles Mendoza   |  last reply

Why do memory modules like flip-flops have a not q output and an r input?

Why do memory modules like flip-flops have a not q output and an r input? What is the necessity of having either? In a d latch the r input is connected to the s input with an inverter, why is it necessary at all? The same goes for not q, if you really needed an inverted q output then you could just add an inverter when necessary. The only thing i could think of is that somehow these are used to connect individual modules sequentially (a 16x4 memory would have 16 rows of 4 bit words; how are the modules connected to form 1 word?) 

Question by seanroberts   |  last reply

1999 dodge ram pick-up can't get the hood open, needs oil help

The guy i bought it from said the hood came up on him a few times, last time it busted the windshield and bent the hinges. He put 2 bolts in it to hold it down , i take the nuts off pull the latch in the cab and nothing happens. Can anyone tell me how to get it open from the outside. Thank You

Question by don cochran   |  last reply

How to? timed latch release

I want to make a box with seperate compartments with doors that will open to release a dog toy, treat etc. at timed intervals. I don't know how to use a timer to unlatch a door. Ideas? thanks - SpleenMa

Topic by SpleenMa 

Latching switch to a momentary switch?

Basically I want to make a toggle switch to trigger a circuit from on or off. its hard to explain but when the switch is in the on position it triggers a circuit momentarily. When I switch the switch off i need it to trigger the circuit again. Its for a 4 wheel drive module for my bronco and its momentary push buttons that I want t o convert to a toggle switch.

Question by catsnw   |  last reply

Gate latch/opener design?

I'm building a fence and having trouble figuring out how to do the latch for a walking/utility gate. I want the fence to be almost seamless from the outside, so with a quick glance you couldn't tell there is a gate right there; however, the gate needs to be able to be opened from the outside with a key. The problem I'm having is that all the hardware I've found for gates use padlocks, so you could only open it from one side if it's locked, and the gate won't be thick enough to use a normal door handle or deadbolt. The parameters are: Opens from inside while locked from outside Outer hardware is minimally intrusive (doesn't stand out much, preferably nothing more than a key hole.) Actual latch can be surface mounted So far the only thing I've been able to come up with is to frankenstein the key half of a deadbolt with half of a turn handle latch I found that forks like a regular door knob but can be surface mounted. The problem is that I am afraid that the spring in the handle will be too much tor just the key to turn and it will wear out quickly. I would appreciate any ideas, and will try to clarify if there's anything someone doesn't understand. Thanks, -rob

Question by siamonsez   |  last reply

SCR latching circuits and LEDs

LEDs and I just can get along...In another project I had a solenoid blowing out LEDs. Now this: I have a number of switches hooked up so they trigger an SCR latching circuit to turn on (and keep on) some LEDs. The SCRs are wired in parallel to each other and have a 1K resistor on the gate. Power is applied to the whole circuit via a timer relay (not hooked to the SCRs). The power is a 12v, 200mA wall wart. And the SCRs I'm using are NTE 5465. The LEDs last a while but burn out or go to a weird blinking state (when the switch is depressed) after about 2-3 days. In my previous project I needed a diode to help with the solenoid voltage spike. But I don't think that it is the case for this project since the SCRs aren't inductive. Do LEDs connected to the switch part of a relay need a diode too? The LED package I'm using is purchased from Happ Controls (see hideous grainy picture). It's rated for 12V but they can't give me a mA rating on them. But they say that no inline resistor is required. Any thoughts? I think this is another case of my inexperience causing me to overlook the obvious.

Topic by robotninjasquid   |  last reply

Single button latching circuit without blinking?

Can you provide a schematic of a latching circuit that doesnt blink when the switch is press hold. Its an issue in this video( )and this video ( that if you hold the switch it will blink. Less components as possible. Thanks for helping have a great day.

Question by Apprentice013   |  last reply

How to make solenoid retract when friction applied.

I have a 12V solenoid that was going to be used in a project with a spring loaded door. It was wired into an arduino project and all was going well. That was until I realised that if the bolt had any friction on it that it would not get retracted when power was applied.I wonder therefore whether there is a simple way of making the bolt retract even when friction is being applied?Alternatively, is there a simple mechanism that could be made where friction can be applied to something else that doesn't add friction to the solenoid bolt itself so that when the bolt is retracted the secondary part is free to move and release the sping loaded door.Any help would be appreciated.

Question by mjolnirofthor   |  last reply

Anyone knows how (or if it is possible) to apply pop rivets to mdf?

I'm designing a carrying case out of 15mm mdf (actually i already have the mdf assembled from a previous project. It's a heavy box, i know, but meh) and would like to add some drawbolt latches to it. The fact is, the latches do have a loop for a padlock, but the hinges and the latches themselves are fixed to the case with screws! That kind of knocks down the whole purpose of having a lock.  The question is: Is it possible to apply pop rivets - or any other kind of rivets - to MDF/plywood/laminate? Thanks!

Question by vinacarv   |  last reply

How to make Ht12d latch output?

How to make Ht12d latch output? I have a project in the making but i dont know how to make a ht12d latch output. I only made a momentary output. Thank you. Have a nice day.

Question by Apprentice013   |  last reply

How to make Ht12d latch output?

I have a project in the making but i dont know how to make a ht12d latch output. I only made a momentary output. Thank you. Have a nice day.

Question by Apprentice013   |  last reply

Latching relay driver from HT12D

I currently have a remote control circuit and its based on HT12E and HT12D but the problem is that I only have a momentary output from it. I want the circuit to latch but also I do not want to use a latching switch in the transmitter. I already tested some of the latching transistor switch that I found online but I can't make it work using the output signal from the HT12D receiver. Thank you and have a nice day.

Question by Apprentice013   |  last reply

Purchasing compression spring latches online

Hi everyone I'm trying to get my hands on some compression spring latches, and have only been able to find them at, but they don't ship to Canada.  The latches I'm looking for are for this instructable: Any ideas where I can find this? I've been scouring the net for a while and can't find anything. Checked out local hardware stores, home depot, lowes, etc, and no luck. Looked at ebay, and can only find some guys from hong kong selling these and they're not made out of stainless steel (which is necessary; this project is exposed to a lot of water). Thx in advance.

Topic by David Catriel   |  last reply

Will this Latching Laser Alarm circuit work? Answered

Hello everyone ^^ I'm here to ask about this circuit. I've been searching for a laser alarm circuit for a long time which locks itself when the beam is broke and keeps the alarm running unless if I want to press the reset button without the use of a relay. Unluckily, I wasn't able to find that kind of circuit in google... AND IT FELT HORRIBLE!!! =O Ahem ahem! Anyway, I've come up with an idea of combining the latching push ON and OFF circuit and the Laser alarm circuit. Will it work? please reply =(      WILL THIS WORK--

Question by Charles Mendoza   |  last reply

Latch-less Non-Perm. Seal?

I have a great passion for lighting things up through the use of LEDs. For one project for school, I took about 40 LEDs and surrounded a "billboard" (3 by 2 foot box made of posterboard - actually looks very nice). While this is good and fun, I ran into a problem. This is not the first model I have made. The very first model was for another project, but with no way to change what was on the "faceplate" (the area the LEDS surround), I was forced to rebuild a second model. Well, I am now required to make yet another copy. But I don't want to recreate the entire billboard, for it takes about 16 hours to build. I instantly came up with the idea of "attaching" other faceplates to it. Velcrow made the most sense - you can remove faceplates, or add new ones whenever you wanted. But velcrow is not affordable at the time. None of my local stores have it in stock, and the soonest any store near me will have it is after Christmas. This due date for the assignment is the 21st of December. I essentially just need to be able to, using as little space as possible (the LEDs only peak through so far), create a way to add, and later easily remove, a faceplate. Latches won't work because it needs to have absolutely NOTHING on the front of the faceplate, for content will be spewed all around the board. Ideas?

Topic by freethetech   |  last reply

Do avalanching diodes "latch up"?

While working and revising my flyback driver design, I had one of the 1N4148 diodes that I was using as protection get cooked!  (it seemed to fail short circuit) I have not tested to see if the MOSFET survived yet. Obviously the diode needs to react fast and handle avalanching energy well. Any suggestions? are some beefy schottky diodes suitable? Also, does making any ordinary diode go into that avalanche or zener reverse breakdown region cause it to potentially lock up and conduct for a period longer than the EMF spikes I'm dealing with? Or with any sort of hysteresis (like when using neon lamps)? Originally my wimpy glass 1N4148 diodes was wired in parallel directly across the MOSFET drain and source reverse biased. However, carefully examining this tesla coil schematic,it appears that there is both a forward biased diode in series with the MOSFETs, and another reverse biased diode(s) in parallel across the MOSFET & diode. It does not look like a bad idea given one the reverse biased diodes can shunt EMF spikes that are too large while the other isolates them from the MOSFET. My only concern is how lossy that would be at 12V operation.

Question by -max-   |  last reply

convert negative pulse into positive using a transistor?

Hello... ive built an scr using transistors to turn on leds in my car with my remote.. my remote uses negative pulse.. now the scr(latching transistor) that ive built turns on with a positive pulse and off with negative.. so turning it off is not a problem.. I need to change the negative turn on pulse to positive to turn it on though. I know theres a simple way using a transistor to do this, but im still learning and my knowledge of transistors is still limited.. here is the schematic I used.. figure 75 b. I followed the schematic and it works just fine..  ... thanks for helping me out here

Question by aclark32   |  last reply

my RTL memory circuit is an oscillator? please help! Answered

Today I soldered together a "D-latch" one bit memory circuit comprised entirely of resistors and transistors. If someone asks me about the schematic, I'll post it. The weird thing about my RTL (resistor transistor logic) memory circuit is that it also works as an oscillator that short circuits my power supply. There is also a slight delay between when i try to set my D-latch's memory state, and when it actually happens.  I have an educated guess that the delay in state change is caused by whatever bizarre mistake caused the oscillation within the circuit. does anyone know of any resistor transistor timer circuits on the web? that may help quite a bit. (lol. EPIC memory pun) the picture above is my device. the oscillation is around 1.2 Hertz. it occurs when the D (data) input of my memory circuit is high. as you can see, this is really confounding me. please help with a comment!

Question by jensenr30   |  last reply

Trying to use relays with a electronic momentary to latching converter. Relays are tripping the latching converter?

I am trying to use this devise,   to turn on a relay attached to a positive wire from a blinker can that sends the signal to the corresponding light. I have two in parallel so I can turn on and off a LH and a RH light with a momentary switch. (can't use a regular on off switch). It works perfectly when attached to its own power supply. I am using this in on a 12 volt system that has some other relays running various things in the system. when I hook this into the system, even directly from the battery, activating the other relays turns the relays on attached to this devise. I suspect it to be noise since it works great on its own power supply. I Tried running the power lead through a resistor and capacitor to help isolate the loop but didn't work. This is stretching my understanding of electricity. What I think I am looking for is how to wire this to isolate it's power +/- circuit from the rest of the system. Otherwise suggestions on how to trouble shoot. I know it is best to add a diagram but I don't know how to make one.

Question by msumrell   |  last reply

Help need Latching Momentary Switch Circuit?

I need to make momentary switch turn on a led and stay on until i hit the switch again. i found a ciruit that i think will work but im having trouble getting it to work

Question by blademaster2444   |  last reply

latch with timed variable reset using transistors

I made a 555 t flip flop and it works nice (i use it as a light switch in my room), but i would like to add another button, whet i pres it would turn the light on  for a time and then automatically off after some seconds to minute. can anyone help me?

Topic by bugijs123   |  last reply

How can I build a latching circuit without a Silicon Controlled Rectifier (SCR)?

I was wondering if there was a way to build a latching circuit without using an SCR because, after all, you can't get them at your neighborhood Shack, and I was wondering if you could use a couple of transistors or something similar.  Thanks in advance  -Julian

Question by jules15   |  last reply

Anybody got a fix for a DS slot-1 latch problem? Answered

My sisters DS slot-1 wont keep the games in. I think the latch is broken. Do i have to replace it for her, like un-solder it and re-solder a new one, or is there a simpler fix?

Question by Redfox888888   |  last reply

help with a transistor circuit that acts like a latching relay

Hello all,, I just joined and this is my first post even though I have lurked here for some time. Now my question. I am trying to build a circuit that behaves like a latching relay. I can build a latching relay from ordinary spdt relays, however im working on a project that is going to require several of them and size is an issue. Im pretty sure a few transistors will do what I want and im sure I could figure it out on my own. I just figured I would ask here to see what kind of answers I get. I don't want any arduio stuff or microcontrollers.. My goal is to keep it as simple as possible and completely solid state and electromechanical.. basically I need it to be triggered by a negative pulse and stay on until a different negative pulse is sent to turn it off.. If possible I want to work into the circuit an adjustable output, either - or + so I can just set it to suite my purpose. It wont need to handle much current, I can add relays to the circuit to handle the higher current stuff.. I have basic to moderate experience and knowledge with electronics so I can understand some terms, but please keep it worded as plain as possible.   Thank You...

Topic by aclark32   |  last reply

Need help with toyota sequoia hatchback stuck shut, please help

I have a Toyota Sequoia that has a problem with the hatchback .  I can not get the door open.  The latch seems to be stuck.  I took off the panel in the inside and still am not able to get the latched open.  Do I need to take the panel under the license plate off to be able to get to the latch?  I have tried everything I can think of to get this door open with the latch.  The door is stuck shut.  Please help me if you can.  I have a childcare and can not be with out this vehicle according to State Licensing laws.  Also can not afford to take it to the Toyota dealership to have it fixed

Topic by marionbuckley   |  last reply

Looking for 120VAC latching relay that can be controlled by low voltage momentary switch

I'm looking for a device that can switch 120VAC lighting and be controlled by a low voltage momentary switch.  This is just a standard residential lighting setup, so I have only 120VAC to the switch box.  I need this device to supply a low voltage signal to the momentary switch that in turn will control the latching relay for the lighting.  The momentary switches I have are low voltage dry contact closure switches rated to handle 32V AC/DC.  Does something like this exist? Thank you for any thoughts you might have on this..

Topic by olif.divad   |  last reply

need help with the latch on my Toyota Sequoia, the door is shut. Can not open.

 I took off the inside panel and still not able to open it.  Do I need to take the panel behind the license plate off also on the out side of the hatch to be able to get to it better?  Please help me with this I need to get it taken care of as soon as possible Thank You  in advance for you help with this problem.?

Question by marionbuckley   |  last reply

Need help with switches.

II have two switches. One momentary and one latching. Both have leds and want to wire them so that the LEDs turn on or off when the latching switch is activated. Please see pictures as they are not regular 2 or 3 poled switches. Thanks.

Topic by bastafari   |  last reply

7 segment sed driver/decoder circuit help

Ive looked all over, and have already tried 3 circuits, but none work. They have either the wrong ic, wrong led display, etc. So, I want to make a circuit that, by using a decoder, I can flip 4 dip switches and make the display make certain numbers. I have a 7447 ic, common cathode led display, but I can only either find a circuit with a 7447 and a common anode, or a circuit with a common cathode but a different decoder (a latch/decoder/driver). Here is the first site I tried: when I finally flip the switches, nothing happens even though I made it exactly as shown. But it has a CMOS, so thats probably a big problem. I also tried this site: it has a common anode, and when I tried it it didnt work. I have exactly ELS321HDB. And I have a power unit that can go from 5 - 18 volts. Can anyone show me how to make this? Im not too good yet at reading circuit diagrams, because I seem to make it way more complex then it should be.

Question by 101yummYYummy101   |  last reply

Programmable solenoid controller

Hi all, I need some help finding a suitable solenoid controller, it must be dc powered and operate a latching solenoid for an hour every 24 hours. It must be programmable by the user and operate the latching solenoid instantaneously on and then off separately. It should be relatively cheap as its for a HNC lawn watering project. Regards woody.  

Topic by woody1001625   |  last reply

Relay Schematic

I have a 1 volt signal that I need to latch open a 12 volt circuit for about a minute. Does anyone have a schematic?  

Topic by Divet   |  last reply

Seat belt fastened circuit

I have designed a circuit the intent of which is to control the seat belt fastened light on the dash.  There are two switches.  1. A pressure switch that closes when someone is in the seat.  2. A Reed switch that closes when the seat belt latch is latched.   Each works correctly separately.  I am using a standard 12V automotive relay to control the light, as below.  Let's just look at one side. 1. When the ignition on the 12V wire connects to the two leads, i.e., the pressure switch and the reed switch. 2. When someone sits in the seat the pressure switch closes and the dash light, which is connected to the relay at 30 and 87A comes on (relay not activated).  3. When the seat belt is latched, the reed switch closes, the relay switches and the current between 30 and 87A turns off. Diodes are introduced in the circuit as shown in the diagram.  The problem is that is does not work correctly.  Sit in the seat and the light comes on.  Buckle the latch but the light does not go off. There is still 12V between 87A and 30, but I don't know why.  I also tried putting a diode between 85 and 86 (pointing towards 86) but that did not help.  Suggestions please.

Topic by DaleR18 

Re: Doubt with interfacing LCD with TMS320F2812

Hi I'm working on TMS320F2812, a 32-bit DSP. I need to interface an a 8X1 LED with my Processor through the GPIO's of the processor. The GPIO's are connected to the LED's through a 74HC273 D-Latch. Can anyone give me pointers on how I must go about the same ?? I have a couple of doubts : 1. My GPIO pins are wired to the D0 to D7 pins of the D-latch. The Outputs Q0 to Q7 are wired to the 8X1 LED Board. My confusion is : how do i ensure connectivity of the GPIO's with pins (D0 - D7) of the latch through Software ( C- routine ) ??? i.e, Do i need to define a structure with the address of D0 - D7 so that I actually realise the connection between them through software ?? Will appreciate if anyone can give me any pointers on how to go about the same. Any sample codes will be of immense help tooo. thanks skn

Topic by skn82   |  last reply

Ikea RAMVIK Coffee Table Arcade Mod

I'm in the purchasing phase to begin building a new arcade modded coffee table.  I have most everything figured out, my only issue is an idea a friend of mine expressed to me tonight and that is a "spring loaded latch" to serve as a means to, when first pushed in, release the monitor from being held in place on the table so it can be more conveniently angled towards the viewers, and when pushed in again, to latch it back into position (flush with table top). My problem is,  I have no idea what these things are called or what they look like. I'm fairly certain "spring loaded latch" is the appropriate terminology, but not completely sure as everything I'm seeing looks entirely foreign to me. I've included a terrible, terrible MS Paint version (I literally spent ~5 minutes on this) to kind of show what I'm going for. I want it flat on latch, angled at release. Spring loaded to push it forward upon release, but locking at the end point (say 35 degrees). This will be my first mod, and I absolutely HAVE to do it as my wife thought it was cool enough to allow for our living room piece. So, to reiterate, my question is: What is the name of this piece that latches/releases upon pressing? Is there one viable for something as heavy as this monitor (21.5" IPS LED Monitor)? --- Also, if anyone has any suggestions, please do share. I am a total novice but my father is a woodworking aficionado (though my intent is to keep this as exclusive to my own efforts as possible).  When I finish this piece, I will absolutely include a step-by-step instruction PDF. Thanks, Eric

Topic by bowserpunch   |  last reply

Bluetooth module without arduino

I want to use bluetooth relay module without arduino , relay continuously energized until circuit turned off or else i turned off from mobile, and second thing if i turned off the bluetooth on mobile it does not affect on circuit

Topic by PrinceS104   |  last reply

Suggestions for a sensitive, hall effect sensor to be used with an arduino?

I'd like to find the an inexpensive, highly sensitive hall effect sensor.  One that could possible sense a strong magnet from several inches away or within someone's hand if they were holding a strong magnet in their closed fist. I am looking for a non-latching sensor that would trigger when a magnet is in the neighborhood - say at least 6".  So the range and shape of the field of detection is important. Imagine that we're playing a game of "which hand is the strong rare-earth magnet in?"  I have a small hall-effect sensor hidden on my palm.  What type of non-latching hall effect sensor would pick up the field through the hand from a distance of about 6 inches or more?

Question by konjurer   |  last reply

My hood release cable broke off, on my 2001 Corolla.

I intend to jack the car up high and put it on jack stands so I will have some room to get under the rad to get access.  I am a 6ft 250 pound male, so my arms are not skinny or super flexible.  Think forearms like Popeye.  I have a lot of hand tools, including boxend metric wrenchs that click like a socket in as little as 5 degrees.  This is what I think will with some sort of extension handle allow me to unbolt the entire latch assembly.      This will likely be a slow and frustrating process, there has got to be a better way, so handy people show me a better way.  Thanks in advance Phil aka zipperboy, adventureboy7 etc.

Question by zipperboy   |  last reply

Need help with using a wireless doorbell ? Answered

I am looking for a way to use a wireless doorbell such that when I press the button a small 6volt motor will go on and stay on until I pressed the button again.   Seems I need a latch relay but the more I research the more confused I get.  Thanks?

Question by duboisvb   |  last reply

Which pins are which on a shift register? What pins on a 74HC595 shift register are the data, clock, and latch pins? Answered

I just bought an arduino and was trying to do this tutorial . I have hit some trouble though and I am confused when it comes to the shift registers. When he says to connect to the clock pin, do we connect to the SCK (Shift Register Clock Input) or the RCK (Storage Register Clock Input)? When he says to connect to the data pin, do you connect to the SI (Serial Data Input)? Also what does he mean when you say to connect to the latch pin? The data sheet for the Digikey shift register I am using is in the link below.

Question by Stoned   |  last reply

I have a Sargent 5131 mortis lock and the flat spring has broken. Is there somewhere i can get one?

The lock has a flat spring, not like the round type springs, and this flat spring keeps tension on the latch to keep it out.  The spring broke and is there a place where I could get another.  Thanks

Question by browne   |  last reply

connecting a breakout board to a strip board

Hi.  A basic question; I need to connect a breakout board to a strip board. What is the best method?  PCB Latch plug header? I have tried putting a wire through the strip board, through the breakout board and then soldering into place, but I do not get good connectivity.  Any help is much appreciated.

Topic by NathanDavey   |  last reply

Chaining 4 74HC595 shift registers together

I have a question about chaining 4 shift registers together.I am going to be sending data to four shift registers and my question is this, when all four are loaded and latched if I send more data is it possible to only send data to the first register in the chain without the others losing their values?

Topic by mbcharney   |  last reply

Comparator doesn't work as expected? Answered

Hello, I'm having a strange problem with the LT1016 ( When the -input is at 0.630V, and the +input is at 0.555V, and the comparator is fed with 5V, the outputs are because of some reason Q(inverted) = 2.10V and Q = 2.67V 2.67V for Q is just out of specifications (minimum High voltage of the pin should be 2.7V). 2.10V for Q(inverted) is not good as it should be less than 0.3V in it's low state. The "latch enable" pin is grounded. Both output pins are not connected. Why doesn't Q(inverted) go to 0.3V and Q to 3V, as the datasheet suggests? I tested this with another (also new) comparator; also an LT1016, and it behaves exactly the same. Pins: 1 V+ 5V 2 +IN 0.555V 3 -IN 0.630V 4 V- 0V 5 Latch Enable 0V 6 GND 0V 7 Qout 2.67V 8 Qout(inverted) 2.10V Any ideas?

Question by DELETED_Electorials   |  last reply