The 50mA is a better max, as the 70mA is an absolute max spec, not a recommended current level.
#AUTODESK CIRCUITS SIMULATOR#
You need to use a minimum of 330 ohm segment resistors, to get to less than 10mA per pin to meet the 70mA abs max limitation in the datasheet, or 470 ohms per segment to meet the 50mA limitation the simulator wants. Although 220ohm gives you 15(ish)mA per segment, which is OK per output pin, the total number of segments is too much. The HC595 package has a 70mA total limitation on the current in the ground and VCC pins. Make them larger, and you can do away with the 100ohm cathode resistor. Those 220 ohm segment resistors are too small.
Thanks again! And sorry for the long rant.
And why would it be alright for digits 1, 4, and 7?Ĭhecking some diagrams online, I can see variations of essentially the same thing, such as this one (with no resistor to the common cathode), or even one in a robotics site with just two 220 ohm resistors to the two common pins only.Īre all three ways of doing it (segments only, common pins only, both) correct? How exactly do they differ? All others would display fine without anything blowing up.Ī) Why is it not enough to add resistors to each of the anodes?ī) Can the circuit work the same with just a large enough resistor on the common cathode?Ĭ) Why does Autodesk Circuits say that the clock / latch pins in the shift register can only take 2.2V? The register's data sheet seems to indicate it can take up to 6V digital signal. Oddly enough (to me at least! it may be obvious to someone more experienced than I) this would happen only for digits 1, 4, and 7. You can see the breadboard and the schematic in here, as well as the program I'm running:īefore I added the 100-ohm resistor to the display's common ground, the simulation would tell me that the shift register would break, as:Ī) The current going through the power pins was too high (70ish mA when a max of 50 mA could be used).ī) The voltage to the DS, STCP, and SHCP pins was too high as well (5V, the max being 2.2V) I have used Autodesk Circuits to test the circuit before I build it. I am attempting to use a 74HC595 shift register to control a seven-segment display with Arduino using only three pins. I also hope the question is not too wide, and would like to thank you in advance for spending your time reading it. Plus, those Circuits.I am very, very new to electronics, so please be patient with me, as I may say something silly. If you don’t have a 123D account, don’t worry, your existing Circuits projects will be merged after you’ve created one on the new Circuits.io page.
Just go to and log in with your Autodesk 123D account. This program is excellent for beginners and experts alike, and we could not be happier about officially being on the same team.Įxisting Circuits.io and 123D users will both get the benefits of the ecosystems. With this acquisition, our users will now have integrated access to all their favorite online design tools, from 3D design and printing to circuitry, without ever having to leave the 123D site.įor those unfamiliar with 123D Circuits, this app enables people to design electronics online and repeatedly iterate on project ideas without encountering real-world obstacles.
#AUTODESK CIRCUITS FREE#
We’re excited to be a part of the excitement this year by announcing that Circuits.io is officially joining the Autodesk 123D family as 123D Circuits!ġ23D Circuits will be joining the the free 123D apps on the digital workbench, making it easier than ever to get creative. Every January, the Consumer Electronics Show (CES) hosts a cornucopia of new and futuristic products that are unleashed to the tech-hungry public.
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