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Alarm Clock Kit

Code: N21FL

3.1  out of 5 based on 8 reviews
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  • Works like a normal digital alarm clock
  • Built-in buzzer
  • Requires a 9V-18V power supply

Product details

Alarm Clock Kit

• Works like a normal digital alarm clock• Built-in buzzer• Requires a 9V-18V power supply


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8 of 8 Reviews

  • Clock works at last

    Not a difficult build but you'll need a fine bit soldering iron. My first attempt wouldn't work because the crystal failed to oscillate (which seems to be a common problem) so I got a second kit and built it a little less neatly. The two caps that strap the xtal to ground were assembled with one snug to the board and the other quite high off the board with the legs untrimmed. This degree of asymmetry seemed to do the trick and it worked first time.

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  • easy to put together works good { bad point kills 9 volt batterys in 2 days ,,must have constant voltage supply}

    Was this review useful?  Yes No  1 1

  • This kit is easy to build, and works exactly as promised. The crystal oscillator started (as they all do) without any problem (if you can solder the parts in the right place). It doesn't (as another reviewer suggests) depend on PCB traces to start. It relies on the gain of the logic gates inside the main chip and the crystal's resonance. The clock does suck power like a fury and the regulator does get hot if you try to power it from anything other than about 9V (and not less than 8V). Don't try to run it long term from a battery. Use a good quality 9V plug-pack.

    Was this review useful?  Yes No  1 1

  • When I was around 10 years old I assembled a digital clock kit with LED display, it was fun and the experience influenced my career choice. I bought this kit for my 7 year old boy who after a few minutes of coaching soldered 90% of the kit by himself with me watching over him. I have couple of 5V power supplies around so I by passed the polarity protection diode and the voltage regulator to make use of them. The disappointment came when I powered on the assembled circuit and there was no display. I checked the voltage and stuff and all looked ok. Probing around I found that when I touch the pins connected to the clock crystal there is some activity on the display, this was big enough clue for me to fix the problem and everything worked well afterwards. The problem was that the crystal was having trouble starting as the impedance on both legs of the crystal was probably a very close match where as the crystals require a slight imbalance to start properly (usually that imbalance is provided by the pcb traces). The fix was to change either C1 or C2 with a different value capacitor, I replaced C1 with a 27nF capacitor and all was well after that.

    Was this review useful?  Yes No  3 3

  • This is a great little kit and works very well. The assembled clock is easy to use and accurate. The kit includes all components but no case or power supply. It includes a generic set of guidelines for building kits and a brief set of specific instructions. A reasonable level of soldering and the basics of component identification is required, so this probably isnÔÇÖt suitable for an absolute beginner ÔÇô or at least not without some help.

    ItÔÇÖs a shame that a basic circuit description and diagram is not included. To me this is an essential part of the learning process, and as an educational kit this should be included. This is the reason IÔÇÖve rated this 4 stars and not 5.

    We found the display very bright over night, so I suggest increasing the size of resistors R1 to R8 (try 470?). It is worth putting a piece of green filter or acetate over the display as it improves the contrast and makes it easier to read.

    Was this review useful?  Yes No  7 0

  • Im no electronics expert but this kit sucks power like there is no tomorrow. It will drain a PP9 in 24 hours and, if run of from a mains supply, the voltage regulator runs hot. This is a badly designed kit. I cannot recommend it.

    Was this review useful?  Yes No  2 1

  • This is a nice easy build, functional and good value. A nice project to run young children through - although no schematic is provided, there is little confusion possible. However the voltage regulator layout was designed by someone with no knowledge of analogue electronics. The use of a small-value ceramic cap for C4 makes the 7805 voltage reg oscillate and run very hot, drawing excess current. The easy fix is to swap the parts used for C3 and C4. Or, if you have some spare caps to hand, you can replace C4 with any electrolytic cap of 1uf or more. Either way you must watch the polarity of the electrolytic cap - it must be installed with the ' - ' marking connected to the 0v side of the incoming supply.

    Was this review useful?  Yes No  6 2

  • It was fun to put together but it didn't work when it as done, no lights on the display light up. I am disappointed with it. :(

    Was this review useful?  Yes No  4 4


Ask a Question

10 of 11 Questions

  • Kev said:

    The green display is very bright in a dark room - Can you offer any advise for reducing the brighntess?

    No sorry this product does not support that.

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  • Mo said:

    Can this be modified so that the clock time does not change when it's being displayed

    No sorry this product does not support that.

    Was this answer useful?  Yes No  1 0

  • Nick said:

    Feedback - the LED display is GREEN, not red. The alarm indicator LED is RED.

    Many thanks for the feedback.

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  • Simon said:

    Can this unit be modified at all

    Unfortunately Maplin are unable to advise on the modification of any of the project kits sold.

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  • tom brown said:

    Hi i need an alarm clock circuit like the one you have - but i need to to go off on a certain date and time, not just the same time each day. I also want instead of a buzzer. it to switch and realy which in tun runs a motor or electromagmnet.

    Nothing we have is suitable I'm affraid.

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  • Jonathan Cox said:

    Can Maplin recommend a suitable 9V-18V DC PSU for use with the N21FL alarm clock kit.

    Try VN10L

    Was this answer useful?  Yes No  1 2

  • Steven said:

    What colour is the LED display?

    This is RED.

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  • sion said:

    can this just be used as a clock without the alarm function?

    Yes the product does support that.

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  • stevie said:

    does it have a plastic outer base

    This is not included

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  • Danny said:

    what are the dimentions of the clock

    Approx 50mm (2") by 90mm (3.5")

    Was this answer useful?  Yes No  2 0

Bulk Prices

Item code Item name Quantity Price
N21FL Alarm Clock Kit (1+) £19.99

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