Maxell CR2032 Battery Backup

Gayan Soyza · Apr 8, 2009

Sorry for the delay mike I was bit buzzy.

Oh my god that DIP-16 is 2.43 USD!!! that is three lunch money.Almost doubled the price of a 18 pin midrange PIC.

Mike - K8LH · Apr 8, 2009

Would a 74HC595 + transistors be a less expensive solution?

Gayan Soyza · Apr 8, 2009

Mike said:
Would a 74HC595 + transistors be a less expensive solution?

Why not its less expensive? But for the UDN1981 cost around 1.2$.Adding 8 transistors is cheap & the design will get bulkier

Mike - K8LH · Apr 8, 2009

I'm not suggesting that you add another IC plus 8 transistors to your current design. I'm talking about your next design.

Use four transistors as "sinking" column drivers and use a 74HC595 and eight transistors as "sourcing" segment (row) drivers. The OE (Output Enable) line on the 74HC595 can be used for full "fade to black" PWM brightness control.

Since you're using sockets for the LEDs, you should be able to install the four column driver transistors underneath the LED sockets, if you need to. The 74HC595 and eight segment driver transistors shouldn't take up too much board space. You might also consider using an SMD version of the 74HC595.

Mike

Gayan Soyza · Apr 8, 2009

Mike said:
I'm not suggesting that you add another IC plus 8 transistors to your current design. I'm talking about your next design.

Use four transistors as "sinking" column drivers and use a 74HC595 and eight transistors as "sourcing" segment (row) drivers. The OE (Output Enable) line on the 74HC595 can be used for full "fade to black" PWM brightness control.

Since you're using sockets for the LEDs, you should be able to install the four column driver transistors underneath the LED sockets, if you need to. The 74HC595 and eight segment driver transistors shouldn't take up too much board space. You might also consider using an SMD version of the 74HC595.

Mike

Hi mike another nice suggestion.Now I remember that one of silicon chip clocks they dim their clocks after 10pm using a similar technic.The sensor they use an LDR.

I prefer this method for 6 digit clock.Let me go through your idea.

Thanks Mike

Mike - K8LH · Apr 8, 2009

I agree that a six digit clock is more useful.

My next six digit clock/alarm/calendar/timer design will be a single small PCB with displays and "diamond" switch pad on the front and with PIC, driver IC, and column driver transistors installed on the reverse side between the LED socket pads.

I'm thinking about using blue or white common anode displays which may need a slightly higher voltage and so the MIC5981 "high side" driver with its seperate VBB supply pin is perfect. You could easily use this chip for driving large 1 foot displays with multiple series LEDs making up each segment.

Mike

audioguru · Apr 8, 2009

Only $2.43/3= $.81 for a lunch??
I buy a cheap lunch for $12.00 and a good lunch for $36.00 plus a tip if the waitress is cute.

Mike - K8LH · Apr 8, 2009

audioguru said:
Only $2.43/3= $.81 for a lunch??
I buy a cheap lunch for $12.00 and a good lunch for $36.00 plus a tip if the waitress is cute.

I've had my fair share of Ramen noodles when I was a poor student (grin)...

mvs sarma · Apr 8, 2009

audioguru said:
Only $2.43/3= $.81 for a lunch??
I buy a cheap lunch for $12.00 and a good lunch for $36.00 plus a tip if the waitress is cute.

It is the same $36+ tip lunch, but it costs less in Srilanka, where 1$=LK.Rs116/-

for around 100/- one gets a good lunch, over there.

Gayan Soyza · Apr 15, 2009

Mike said:
I agree that a six digit clock is more useful.

My next six digit clock/alarm/calendar/timer design will be a single small PCB with displays and "diamond" switch pad on the front and with PIC, driver IC, and column driver transistors installed on the reverse side between the LED socket pads.

I'm thinking about using blue or white common anode displays which may need a slightly higher voltage and so the MIC5981 "high side" driver with its seperate VBB supply pin is perfect. You could easily use this chip for driving large 1 foot displays with multiple series LEDs making up each segment.

Mike

What a clock looks like a novelty design I really like to see.But did you ever think about the power management Mike?

shokjok · Apr 15, 2009

The photo shows four circuit errors:
1. All 150-ohm markings on the PCB are fitted with 220-ohm resistors.
2. There are no colons in the clock display. This resembles an event counter.
3. The 18-pin IC is not identified ( next to the crystal).
4. There is no 4.7K resistor near pin 10 of the 18-pin IC.

Gayan Soyza · Apr 15, 2009

shokjok said:
The photo shows four circuit errors:
1. All 150-ohm markings on the PCB are fitted with 220-ohm resistors.
2. There are no colons in the clock display. This resembles an event counter.
3. The 18-pin IC is not identified ( next to the crystal).
4. There is no 4.7K resistor near pin 10 of the 18-pin IC.

My SSD are so bright so I increased the display resistors than mentioned.

You mean what colons ?

There is no 4.7K resistor near pin 10 of the 18-pin IC.

Its in the ohmic region.I placed an 220R.I already changed in my silk screen.

The 18-pin IC is not identified ( next to the crystal)

Here there are lots of hackers here so better to keep mouth shut whats that micro is

Mike - K8LH · Apr 17, 2009

Hi Gayan,

What do you mean by "power management" Sir?

Maxell CR2032 Battery Backup

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