Hello Gang,
I'm working on a binary clock project...and I've used the DS1307 chip as my RTC...I know the stock crystals / chip give about 20PPM performance, and I understand that can be dialed in a bit by using a variable / trimmer capacitor from X1 to GND on the crystal.
So, I'm wondering...what is the experience out there? What range of trimmer caps should I look for? Any part suggestions? I got a few trimmers from Mouser, but they're surface mount, and I'm afraid too small for me to work with...(Murata 2 - 20 pF 25Volt).
So, I thought I'd go to the source of all knowledge and see what the recommendations are.
Currently, my prototype was clocked running about a second and a half fast per day (which is within the 20PPM tolerance)...with a software adjustment at midnight, I have the tolerance down to around .4PPM...but I'd like to try and use a trimmer to keep the time from slipping so much per day. A second and a half over the course of a day is noticeable when comparing the clock to a reference. I know, as the designer, I'm the only one who will notice it...but geeze!
I'm going to look into the DS3231 for future projects, however, for my own "Because I can" mentality, I'd like to see how dialed in I can get the DS1307.
Thanks!
I'm working on a binary clock project...and I've used the DS1307 chip as my RTC...I know the stock crystals / chip give about 20PPM performance, and I understand that can be dialed in a bit by using a variable / trimmer capacitor from X1 to GND on the crystal.
So, I'm wondering...what is the experience out there? What range of trimmer caps should I look for? Any part suggestions? I got a few trimmers from Mouser, but they're surface mount, and I'm afraid too small for me to work with...(Murata 2 - 20 pF 25Volt).
So, I thought I'd go to the source of all knowledge and see what the recommendations are.
Currently, my prototype was clocked running about a second and a half fast per day (which is within the 20PPM tolerance)...with a software adjustment at midnight, I have the tolerance down to around .4PPM...but I'd like to try and use a trimmer to keep the time from slipping so much per day. A second and a half over the course of a day is noticeable when comparing the clock to a reference. I know, as the designer, I'm the only one who will notice it...but geeze!
I'm going to look into the DS3231 for future projects, however, for my own "Because I can" mentality, I'd like to see how dialed in I can get the DS1307.
Thanks!