theconrodkid
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| posted on 2/10/14 at 10:08 AM |
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lectronics question
Hi peeps,bought one of these 1Pcs DIY Kits AT89C2051 Electronic Clock Suite Electronic Parts and Components | eBay
–°å»ºç½‘页 2
BIDX%3AIT
went to gether pretty well but when i powered it up it came as a suprise that it didnt work  .
it draws a lot of current like there is a short but there is no soldering across the tracks on the back,all the componets are in the right place, the
cap (c1) gets very hot,i removed that and it,s still the same,no workie....any ideas ?
who cares who wins
pass the pork pies
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Nickp
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| posted on 2/10/14 at 10:15 AM |
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No way!!
At £3.31 delivered from China you'd expect it to be spot on 
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loggyboy
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| posted on 2/10/14 at 10:30 AM |
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check each component one by one. Probably silly polarity mistake, like one of those square switches orientated 90degrees, or diode back to front.
Mistral Motorsport
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theconrodkid
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| posted on 2/10/14 at 12:04 PM |
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tis amazing what you can get for your £1 these days isnt it 
i have checked everything on the board and everything is ok,short of removing every component,i think one is duff as my soldering is something to
behold .....might as well just get another one
who cares who wins
pass the pork pies
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theprisioner
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| posted on 2/10/14 at 12:19 PM |
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Sounds like either the 3 pin regulator is miss wired or one of the capacitors is the wrong way round.
http://sylvabuild.blogspot.com/
http://austin7special.blogspot.co.uk/
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Madinventions
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| posted on 2/10/14 at 12:37 PM |
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What power supply are you using? (Plug top/bench/battery, AC/DC, Voltage, Polarity etc)
Mojo build diary: http://www.madinventions.co.uk
Solo music project: Syrrenfor http://www.reverbnation.com/syrrenfor
View my band website:
http://www.shadowlight.org.uk
http://www.eastangliankitcars.co.uk/
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Dale
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| posted on 2/10/14 at 12:54 PM |
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Very easily done to insert the chip 180 degrees out.
check the little notch is at the end for pin 1.
Dale
Thanks
Dale
my 14 and11 year old boys 22
and 19 now want to drive but have to be 25 before insurance will allow. Finally on the road
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rf900rush
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| posted on 2/10/14 at 04:01 PM |
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Post a picture of both sides of your PCB.
Many eyes may see some thing
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theconrodkid
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| posted on 2/10/14 at 06:02 PM |
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thanks for the replies chaps,i am using a 9 volt battery for power,caps are all the right way round,it does it without the chip as well,i have checked
it over several times with a magnifying glass and cant see and bridging...oh well,looks nice as an ornament .
who cares who wins
pass the pork pies
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02GF74
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| posted on 2/10/14 at 06:29 PM |
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7 resistors and 7 transitors, i am guessing the led segments are over driven and multiplexed.
Why 9 volts. The chip is probably a pic and would be 5 v , i dont see anything obvious that is a regulator, unless it is the transistor on the
left.
You have circuit diagram?
How much current is it drawing. Six 7 segment leds when fully on would draw half an amp, typically 10 to 25 mA each.
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gremlin1234
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| posted on 2/10/14 at 06:42 PM |
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quote:
i dont see anything obvious that is a regulator, unless it is the transistor on the left.
that is a 5v regulator I think it shows as
7BL05 which would give 5v,
I would check the output 5v line from that,
ps, my guess is that one of the transistors has be installed instead of the identical looking regulator
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theconrodkid
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| posted on 2/10/14 at 06:56 PM |
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i think Mr gremlin get the cigar.
i was just looking at the transistor shapes and assumed one went there (u1).
still did it with 3X AAA (4.5 volts)...too late and dark now,
02gf74,i will try to send you the circuit diagram
who cares who wins
pass the pork pies
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theconrodkid
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| posted on 2/10/14 at 10:18 PM |
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woooo hooo,we now have the time,thanks guys
who cares who wins
pass the pork pies
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02GF74
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| posted on 4/10/14 at 08:22 AM |
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got the scan.
'tis as I predicted.
The same LED segments in all the 6 displays are connectted together (i.e. bus). They are driven by the chip (U2) with a resistor in series to limit
the current.
The 6 transistors are driven by the chip (U2) that when turned on will supply power to the LED displays.
This multiplexing method means the chip does not need to drive each segment individually and less resistors are required.
To displaly a digit on LED 1, U2 sets the value on the bus and turns on the transistor for LED 1.
For LED 2, the value is set on the bus and the corresponding transistor is turned on and so on.
Note that only one transistor is on at any one time and this happens so fast that you should not see the displaly flash but if you took the board and
waved it, you will see the flashing.
And finally, there is a 5 V regulator U3 and it would appear you fitted a transistor in its place.
BTW for the same price, you can buy in Argos a device with a similar function, ready made, that you can wear on your wrist and whose batteries will
last much longer.
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theconrodkid
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| posted on 4/10/14 at 11:23 AM |
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thanks for all the replies guys,true i could buy something ready made that wuld be reliable but where is the fun in that ?,like building a car
instead of buying one 
who cares who wins
pass the pork pies
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