touch 34 Posted March 17, 2011 Share Posted March 17, 2011 Hi all, I picked up some CD74HC4511 binary to decimal converters to use with my 7 segment displays, however I'm having some issues with them. The problem I'm having is some decimals fail to fully display, for example: I'm sending 0100 (d3 low, d2 high, d1 low, d1 low), that should display a 4, however the G segment on my display is not lighting up, when probing the G LED's pin I'm getting 1.8v, I'm also getting 1.8v when I probe the F pin, pins D and E are 0v as expected, pins F, B and C are 3.5v as expected. Similar things are happening when trying to display the decimal 6, all have their expected voltages, accept the G segment whitch is reading 1.8v. I'm really stumped as to what is causing some numbers to not properly display and the random voltages. Heres the datasheet: http://focus.ti.com/lit/ds/symlink/cd74hc4511.pdf Here is the circuit I've been using for testing: http://hs.doversherborn.org/hs/bridgerj ... addLED.htm The only minor differences I have are that I'm using 5k resistors (out of 10k's, but according to my googleing, 5k's should be fine), and a single resistor on the cathode but that should only cause uneven display brightness. Quote Link to post Share on other sites
RobG 1,892 Posted March 17, 2011 Share Posted March 17, 2011 My guess ESD damage Quote Link to post Share on other sites
touch 34 Posted March 17, 2011 Author Share Posted March 17, 2011 I tried a second chip thinking I had a faulty chip, same exact problems. Would a miss-wiring of the 7 segment cause this? If you put LT low, it's supposed to light all the Segments and that works fine, so I doubt its wired incorrectly. Quote Link to post Share on other sites
RobG 1,892 Posted March 17, 2011 Share Posted March 17, 2011 Is the 1.8V with display connected or not? Quote Link to post Share on other sites
touch 34 Posted March 17, 2011 Author Share Posted March 17, 2011 ah, I forgot it was testing the same way with the display disconnected... So it cant be a display miswiring. Quote Link to post Share on other sites
RobG 1,892 Posted March 17, 2011 Share Posted March 17, 2011 Sounds like pins 14 and 15 or 13 are shorted. Check your circuit, pull out the chip and measure resistance between them. That would explain half Vcc when g is high and other pin low. Also, in your original post you stated first that F is 1.8V but than later that it is 3.6V. So, which segments are missing when you display 4 and 6? touch, gatesphere, jsolarski and 1 other 4 Quote Link to post Share on other sites
touch 34 Posted March 17, 2011 Author Share Posted March 17, 2011 You're exactly right, there was a tiny short... I don't know why I didn't think of that. I had etched some breakout boards (these are SOIC16 chips), there was a hairline piece of unetched copper connecting the two traces. Thanks! Quote Link to post Share on other sites
RobG 1,892 Posted March 17, 2011 Share Posted March 17, 2011 It's always the little things. Quote Link to post Share on other sites
GeekDoc 226 Posted March 18, 2011 Share Posted March 18, 2011 Nice job, Rob. Quote Link to post Share on other sites
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