Questions regarding Real Time Clocks (RTCs) which can be a timekeeper IC used by microcontrollers, or using a microcontroller as an accurate timekeeper. Some have calendar, alarm, interrupt or heartbeat features, while some simply keep track of time since last programmed (Epoch timers are similar).
9
votes
6answers
901 views
What happens if I omit the pullup resistors on I2C lines?
Just now I realized that the I2C data and clock lines (SDA and SCL) must have pullup resistors.
Well, I've built a couple of clocks using the DS1307 RTC (see datasheet) according to the schematic ...
0
votes
2answers
44 views
Synchronize RTC of 2 different MCU's [closed]
I have 2 different microcontrollers and I need to use their internal RTC. however I need the 2 RTC's to be in sync when they are used. How would I achieve something like this?
1
vote
1answer
98 views
Switching Arduino/ATMega to sleep mode when on battery
I'm trying to make a small clock but want to ditch the need for a separate RTC chip with battery backup. What I would like to do, instead, is keep track of the time completely on the ATMega using the ...
1
vote
1answer
188 views
Designing a large 7-Segment display
I'm trying to design a product that have the following features for mass production, and I'm asking from your experience, how to get the lowest price for the components, quality of the chips in terms ...
1
vote
1answer
112 views
How to modify DS1307 RTC to use 3.3V for Raspberry Pi?
I bought DS1307 RTC but it is 5V so it can't be connected to the Pi. I know it can be modified to use 3.3V by removing 2 resistors. This sensor is different than the adafruit kit so I am not sure ...
2
votes
1answer
134 views
Real Time Clock DS1307 interfacing with Arduino Uno
I am currently working on an electronics project of building my own Digital wall clock. For that I tried making a RTC module with DS1307 IC.
I followed the following instruction from this website.
...
2
votes
2answers
173 views
What is the purpose of the capacitor in this schematics?
I am trying to understand a RTC module from Sparkfun.
I don't understand the purpose of the capacitor in this circuit.
Here are the
procduct's page and the schematics link.
Can some one please ...
3
votes
0answers
87 views
Sanity check: Using the DS3231 as a clock source for uC
The DS3231 is an RTC chip with an onboard temperature compensated oscillator and 32kHz output. I want to use this chip in a small clock project I'm designing because I've got a couple lying around. ...
2
votes
1answer
82 views
Working with a BQ4285 RTC from Texas Instruments
I recently acquired a BQ4285 Real-Time Clock manufactured by Texas Instruments... And I have one major problem! I have little idea how to use it.
I am trying to connect it to an Arduino Mega 2560, ...
2
votes
1answer
314 views
How long will a DS1307 RTC run on a CR2032 coin cell battery?
I have a homemade clock based on an atmega328 and a DS1307 Real Time Clock. When off, the DS1307 is powered by a 3V CR2032 coin cell, as usual.
If I leave the clock off most of the time, how long ...
3
votes
2answers
186 views
Could these ICs from Alibaba be counterfeit?
I'm trying to source some parts for a kit and the most expensive part I have by far is the DS1307+ RTC chip. They run about $4 in single buys and $1.96 in larger quantity.
But then there's this: ...
5
votes
1answer
227 views
How to improve I2C RTC accuracy
I´m using a PCF 8583 I2C RTC for one of my projects (i´m not a professional, just an amateur). The clock delays about an hour per day, which I find unacceptable.
I´m using a 32768 Hz, 12.5 pf, 50 ...
-1
votes
0answers
179 views
PIC : Internal RTC stop when i read time during some operation
Hi I am using PIC18f67k22 controller.I am using internal RTC.
I am try to read RTC time at start of RTC. After some time read back time of RTC and It was fine but problem is when i am reading ...
1
vote
1answer
190 views
PIC : problem with initialize internal RTC of PIC18F67k22.
I want to initialize internal RTC of PIC18F67K22 with some fix time&date.Time is set properly but date is not set properly.problem occur in setting year.year is not set to whatever we give to ...
-1
votes
0answers
103 views
how to synchronize internal RTC to computer time and date
i am using pic18f67k22 controller.i already configure and initialize internal RTC. But i want start RTC to computer time.so how i can synchronize pic RTC to computer.i have one computer application ...
3
votes
3answers
351 views
Turn on arduino with RTC Alarm
I would like to have a RTC alarm turn on my arduino at a specified time each day. I know that Arduino has good sleep modes but I'm concerned even with the quiescent power consumption from the voltage ...
1
vote
1answer
101 views
How do I configure a external RTC that uses 3-wire SPI for the LPC 2387?
Here is the link to the datasheet of the RTC PT7C4302.
I can do it with MISO, MOSI, but SISO I have no idea how to do. Some similar code examples would be great.
0
votes
1answer
633 views
RTC on MSP430 microcontroller with 32.768kHz crystal and low power
I need to set timer to interrupt every second. I'm using 32.768kHz external crystal with MSP430G2553 MCU. The setup should consume < 10μA.
I tried this code but it consumed 80-90 μA.
What am I ...
2
votes
2answers
305 views
Does polling a DS1307 too frequently affect accuracy?
I did some research, and I found contradictory response on the web. I'm polling a DS1307 on an loop, with an Arduino, that takes about 20 ms to run, so basically I'm polling the I2C interface 50 times ...
0
votes
1answer
244 views
ds1307 drift too big
I have a RTC ds1307 mounted on a prototype board ( the one with 3 pin stripped ), and I'm experiencing a delay of about 5 sec/day, far too big compared to some research I did. Can that delay be caused ...
6
votes
3answers
589 views
How to calculate day of the week for RTC?
I am using MCP7940 RTC from microchip it requires to enter the day of the week as part of updating RTC with date. So how should I calculate day of the week based on the date provided by the user ?
0
votes
2answers
174 views
How to Synchronize two RTC module one internal and other external?
I am developing a data logger based on PIC controller. The PIC has internal RTC but does not have pins for connecting battery so I am using pic's internal RTC to generate interrupt every second and ...
1
vote
1answer
236 views
I2C with DS1307 hang after end of transmission
I've got a home brewed RTC with DS1307. I've put two pullup resistors on SDA and SCL lines, connected them to the Arduino 5 and 6 pin respectively. I've also provided a backup battery since I read ...
0
votes
1answer
554 views
Is there any Real time clock (RTC) which provides time resolution in microseconds?
I've been searching for high precision RTCs on Google but almost all RTCs like DS12C887, DS1307 provide time resolution in seconds which is ok for general use. But is there any RTC IC which can ...
1
vote
2answers
393 views
DS1307 RTC not working with rweather library
I'm using the DS1307 RTC together with arduino and this library
http://rweather.github.com/arduinolibs/classDS1307RTC.html
When i power the chip directly from the 5V and GND outputs from my arduino ...
1
vote
1answer
121 views
Using alarms with the DS1307RTC
I'm trying to wrap my head around following library:
http://rweather.github.com/arduinolibs/classDS1307RTC.html
I can see that the DS1307RTC has a writeAlarm and readAlarm function.
I'm not sure how ...
4
votes
3answers
289 views
DS1307-breakout-board
I want to build an RTC clock for the Raspberry Pi. Adafruit has a guide to accomplish this with Dallas DS1307. On the schematic they put a 2.2K resistor between VCC and SCL and do the same for VCC and ...
1
vote
3answers
755 views
Two wire vs. three wire serial interface for RTC
I'm looking to choose an RTC for a project I have in mind.
I have the following options (linked to datasheet):
DS1307
DS1302
The main difference seems to be the communication protocol. The DS1307 ...
1
vote
1answer
109 views
DS3232M Skips seconds when writing to SRAM
I'm using a DS3232M that works great for keeping track of the time until I try to write to the SRAM on the chip. When I use the SRAM it slows the updates of the seconds register or stops them all ...
1
vote
1answer
269 views
Multiple masters for i2c device
I have a DS1307 RTC chip that I want to interface with multiple masters.
One, an ATMega chip, will only ever really need to pull time data from the chip and the other (probably just an ATTiny) will ...
4
votes
2answers
457 views
How does GPS calculate time
How can a GPS device give exact timing even when the number of available satellites are zero?
I'm monitoring GPS data using VisualGPS.
5
votes
4answers
1k views
DS1307 power failure problem
the DS1307 has two power sources the main VCC source and the back up battery, which must feed the DS1307 when the power goes down and keep timing and here my problem,
I am facing a problem with the ...
1
vote
1answer
366 views
RTC on a circuit board and little green disk 00504 [closed]
I have a 110 volt powered mini fridge. after replacing a board soldered fuse with a replaceable set up I have discoverd a component that looks similar to a capacitor disk that is cracked. the fuses ...
1
vote
2answers
199 views
Ground copper pour for Crystals and Real time clocks
I am laying out a (2-layer) board, with a standard SMD Crystal as well as a Real-time clock placed on the top-side of the board.
What are guidelines regarding ground copper pour under the Crystal and ...
2
votes
2answers
640 views
Is case grounding compulsory in typical 32.768kHz crystal for Real Time Clock?
Pictures shown below is a typical 32.768kHz crystal, commonly use in Real Time Clock circuit (e.g: DS1307 & DS1337)
Referring to an earlier question posted here, it is a good practice that ...
2
votes
2answers
217 views
Device including RTC EEPROM and battery?
I am currently designing an electronic board and i got a question:
Do you know if there is any device in which are integrated an RTC, an EEPROM and a battery? I heard about this type of device (i ...
9
votes
3answers
2k views
How do you Calibrate 32.768kHz crystal for PIC24 RTCC
I'm trying to figure out the best method for PIC24 RTCC crystal calibration.
Their application note states two methods: using a lookup table and using a reference system clock.
According to them the ...
3
votes
4answers
298 views
RTC clock skipping months back
I will come to a question further down, but first a little background
We are struggling with reproducing a nasty bug that we have been getting reports for.
The symptoms clearly show that the RTC (a ...
7
votes
2answers
1k views
supercap-powered RTC?
I'm designing a ATmega-based microcontroller test board. One of the features I want to include is a Real Time Clock with a Maxim DS1307 IC. Instead of including a traditional coin cell battery backup, ...
3
votes
1answer
141 views
How to sync sensor data
Suppose I have multiple dataloggers receiving sensor data, how can I sync those signals afterwards? The most obvious way would be adding timestamps to the data, but they have independant clocks, so I ...
0
votes
2answers
1k views
PIC32 RTCC running too fast 1min = 10 sec
I'm having problems with the clock settings on my PIC32.
One minute has a duration of 10s with the current settings.
Does anyone know where I have to change my settings?
Here's the code:
// ...
2
votes
1answer
516 views
Fix a vintage computer (IBM PS/2 55SX) without a DS1287 Real Time Clock
I want to reanimate an a old vintage computer, the IBM PS/2 55SX.
The dead component is the DS1287 Real Time Clock (in particular, the battery inside).
Is it possible to simulate with a BASIC Stamp ...
0
votes
1answer
737 views
PIC32 + RTC via SPI doesn't work
I'm trying to read the time from an RTC with my PIC32 Microcontroller via SPI.
I've already succeeded in reading the time with an Arduino from the RTC.
PIC32: http://www.sparkfun.com/products/9713 ...
4
votes
2answers
667 views
DS1307 RTC Debug
I'm having trouble with getting the DS1307 RTC to work. I'm talking to it via an Arduino, and I'm just trying to get an example sketch to work. I've tried two different libraries - one from Ladyada, ...
5
votes
1answer
277 views
MCP79411 not “ticking”
I'm using the Microchip MCP79411 Real Time Clock. I can communicate with the device, read the MAC address from it, write to the EEPROM function and read back those values, but the Time and Date ...
3
votes
2answers
453 views
Are there RTCs with 100Hz output?
All RTCs I've seen so far operate from a 32.768kHz crystal, which can't be divided to 100Hz. Are there 32.000kHz RTCs?
7
votes
6answers
2k views
Why do real-time clock chips use BCD
I have seen dozens of different real-time clock chips on the market, as well as a number of processors with a built-in separately-powered real-time clock module.
Nearly all of them not only store ...
4
votes
1answer
220 views
Do I need an accurate clock for an accelerometer?
I am working on a project where I want to get very accurate data from an accelerometer. I plan on sending my data over bluetooth to be interpreted by a computer.
I am assuming that bluetooth will ...
1
vote
2answers
1k views
DS1302 Real Time Clock Question
So I am attempting to tie a real time clock (DS1302) into an Arduino and then eventually a AVR chip directly. From all of the schematics I have seen, it appears a crystal is required. I read through ...
4
votes
3answers
1k views
Smallest lithium battery backup?
I'm considering putting a small lithium battery on my Super OSD Pro boards. The battery would provide power to the RTC. I am wondering how small can you get a battery? I don't really care about ...
