20 Minutes Timer 20 Minutes

[Hortense Malovich]

Setthe hour, minute, and second for the online countdown timer, and start it. Alternatively, you can set the date and time to count days, hours, minutes, and seconds till (or from) the event. The timer triggered alert will appear, and the pre-selected sound will be played at the set time.

I'm trying to light a led using bluetooth and then have it on for 3 minutes, then turn off. The problem is with the "timer", it dosen't turn off after 3 minutes (180000ms). Can anyone se what i'm doing wrong? I have just started programming so please be nice

I could use a timer and set its interval to 1000. Then within its tick event, I could check the clocks current minute against a variable that I set, if the minute has changed then run my code. This worries me because I am making my computer do a check every 1 second in order to carry out work every 1 minutes. Surely this is ugly ?

Simply compare the value of Environment.TickCount or DateTime.Now to the last stored time (the previous 'minute tick'), and you should have a reasonably precise solution. The resolution of these two time values is about 15ms, which should be sufficient for your purposes.

Do note however that the interval of the Timer control is not guaranteed to be that precise or even anywhere now, since it runs on the Windows message loop, which is tied in with the responsiveness of the UI. Never rely on it for even moderately precise timing - though it is good enough for firing repeating events where you can check the time using a more sensitive method such as one of the two given above.

A clock implementation would simply create the class with a interval of 1 second and listen to the event. Be wary though that this is a real-time clock, if the tick event takes longer than the interval to finish you'll notice that the clock will try and catch up to real-time this will cause a burst of tick events being raised.

You would fire the short interval timer only until the desired start time of the main interval timer is reached. Once the initial time is reached, the second main interval timer can be activated, and the short interval timer can be deactivated.

Alternatively, you could sleep to pause execution until it times out which should be close to your desired time. This will only wake the computer when the sleep finishes so it'll save you CPU time and let the CPU power down between processing events.

Use a timer set to run every second (or millisecond, whatever your accuracy threshold is), and then code the method to run your functionality if and only if the current time is within that threshold past the "on the minute" point.

What I'm using for scheduled tasks is a System.Threading.Timer(System.Threading.TimerCallback, object, int, int) with the callback set to the code I want to execute based on the interval which is supplied in milliseconds for the period value.

I am using this approach for my dynamic timer. From the input_number in minutes, convert it to seconds and using the timestamp expression to convert it to the duration time format. See if you can use the same approach to get yours to work.

I am trying to figure out the limit between the free offerings and the enterprise. I heard that there was a 20 minute limit but what does that mean? I do do not see any counters in my account nor projects.

I just started a project with about 540 images. so far so good. I was curious if the project will just fail if it gets too large? FYI, this is a dorky meaningless project. We would never ask for extra time on this. I would just like to know how far I can go.

The 20-minutes limit applies per job.

You can reach this limit when your dataset is pretty big and/or your NN architecture is complex and needs a lot of epochs to converge properly. Most of the time it happens on Object Detection projects but I also have seen the limits been reach on image classification and audio projects sometimes.

I would like to use LPTIM1 on my STM32L0 to make it wake up (the micro is in Stop Mode) after 5 minutes but I don't know what is the best configuration to do that. Currently I have the configuration below.

if this timer is your only option, set up the mcu to wake up at certain interval, like roll-over. In the isr, increment a counter and test if certain number of roll-overs has been achieved. Essentially that counter forms your most significant bits of the timer.

The Pomodoro Technique is a time management method developed by Francesco Cirillo in the late 1980s.[1] It uses a kitchen timer to break work into intervals, typically 25 minutes in length, separated by short breaks. Each interval is known as a pomodoro, from the Italian word for tomato, after the tomato-shaped kitchen timer Cirillo used as a university student.[2][1]

Apps and websites providing timers and instructions have widely popularized the technique. Closely related to concepts such as timeboxing and iterative and incremental development used in software design, the method has been adopted in pair programming contexts.[3]

The stages of planning, tracking, recording, processing and visualizing are fundamental to the technique.[1] In the planning phase, tasks are prioritized by recording them in a "To Do Today" list, enabling users to estimate the effort they will require. As pomodoros are completed, they are recorded, adding to a sense of accomplishment and providing raw data for subsequent self-observation and improvement.[1]

The creator and his proponents encourage a low-tech approach, using a mechanical timer, paper, and pencil. The physical act of winding the timer confirms the user's determination to start the task; ticking externalises the desire to complete the task; ringing announces a break. Flow and focus become associated with these physical stimuli.[1][8]

A few days ago I purchased a single ticket from Cologne (Kln) to Aachen via the DB Navigator app. The ticket was valid for 6 hours after the purchase, however a timer started from 00:00 and stopped at 02:00 as seen on the image below.

According to this link (only in German), it is to check if you have bought the ticket just right now or a sufficient amount of time before. The rules usually are, that you have to buy a ticket before you get on the train. Now, with mobile tickets, some "clever" people thought, they just need to buy a ticket when they see the conductor, and to ride free when they don't see one. In local transit (especially trams, and more and more regional trains) you don't have a regular conductor in every train anymore, but just ticket checking teams, which go around the city. Obviously they can only cover a small part of the available transit vehicles.

This is most likely the reason why the operators introduced this timer, so that it's visible for the conductor if you have bought the ticket just right now or more than 2 minutes ago.

@dunni's answer describes the attack that this security measure attempts to mitgate. A comment on his answer claims that this is "security theatre"; I describe in this answer (because this explanation is too long to fit into a comment) why it is not.

Most security measures cannot completely prevent attacks. An effective security measure is one that increases the cost to the attacker significantly while not also increasing costs to the defender beyond reasonable economic return.

This is why spot checks for tickets work though they sometimes allow people to travel for free: though an attacker can simply not buy a ticket and stand a chance of gaining free travel, if the penalty when this is discovered is high enough most potential attackers will choose to buy a ticket rather than run the risk of paying the fine or suffering other punishment

In this case, there are two requirements for an attacker:1. Write or obtain a version of the app in appears to be the official one and which displays the same result as if the user had purchased the ticket well before the conductor arrived to check it.2. Side-load this app, since Deutsche Bahn can fairly easily ensure that one appearing in the official store is easily taken down.

Writing such an app is significantly difficult; it involves not only having the skill to duplicate the app itself, but also overcoming any security measures protecting the original app (such as being able to extract any necessary keys from it necessary to instruct the DB servers to purchase a ticket).

Of course, once even one person writes such an app, it could be shared with others incapable of doing so. But finding such an app once it's written is also not completely trivial; DB also may have the ability, even if it's not on the official store, to get it taken down through legal means. If they can't do that, they can also easily change how their app works (different security keys, different network protocols, different display) to require the app's author to update it.

Even should the app be easily available, the user still needs to be sophisticated enough to side-load the app (since it won't be available from the official app store) and must also be willing to run the personal security risk that the app author is malicious and actually wrote the app to attack the users who download it, rather than DB.

All of the above combine to make a fairly high cost to the attacker, whereas for DB to add the timer to their existing app is very little work. Spending a few days of developer and tester time to add this feature to the application thus probably pays itself off very easily even if it prevents only 50% of the potential attackers from executing the attack (though it probably prevents a far higher percentage).

The reason something like American TSA security checks qualify as security theatre is because they impose very large costs on the defenders for very little gain against attackers. These checks exist because the costs are mainly borne by people who can do little about it (airlines and their passengers) whereas the benefits (looking like you're doing something about a problem) accrue only to some government and elected officials who suffer little of the overall cost.

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