Output pins on an Arduino do not provide much current. They are limited to 20mA which is enough to power a small mechanical relay or several indicator LEDs. In some cases, this is great news because applying 5V to some LEDs will burn them up in a second or two. However, if something more substantial needs power and control an interposing device must be used. An interposing device can be a mechanical relay or a solid-state relay but very often a humble transistor is the best choice. Some of the outputs in this circuit need more power than the available 20mA so transistor circuits were designed yesterday but they needed to be built and tested.
For comparison, four identical LEDs were added to the two breadboards. The board on the left used the transistor circuit while the board on the right pulled all the power through the Arduino.
Differences between the outputs were not as obvious as I had hoped. The transistor circuit does take strain off the Arduino, which should increase longevity and reliability but the bare IO pin did a good job of supplying power. Due to the low cost of the transistors, it seems like a logical choice to keep them in the circuit.
The resistor values used to protect the LEDs on the transistor circuit were a guess at first. After calculating the ideal value brightness increased again and on a whim, a short was created for no resistance aside from the transistor. This dramatically increased the brightness.
Downloads:
The rest of the posts for this project have been arranged by date
First time here?
Completed projects from year 1
Completed projects from year 2
Completed projects from year 3
Disclaimer for http://24hourengineer.blogspot.com/ and 24hourengineer.com
This disclaimer must be intact and whole. This disclaimer must be included if a project is distributed.
All information in this blog, or linked by this blog, are not to be taken as advice or solicitation. Anyone attempting to replicate, in whole or in part, is responsible for the outcome and procedure. Any loss of functionality, money, property or similar, is the responsibility of those involved in the replication.
All digital communication regarding the email address 24hourengineer@gmail.com becomes the intellectual property of Brian McEvoy. Any information contained within these messages may be distributed or retained at the discretion of Brian McEvoy. Any email sent to this address, or any email account owned by Brian McEvoy, cannot be used to claim property or assets.
Comments to the blog may be utilized or erased at the discretion of the owner. No one posting may claim property or assets based on a post.
This blog, including pictures and text, is copyright to Brian McEvoy.
2017-05-01 (M)
For comparison, four identical LEDs were added to the two breadboards. The board on the left used the transistor circuit while the board on the right pulled all the power through the Arduino.
Side-by-side comparison of circuits
Differences between the outputs were not as obvious as I had hoped. The transistor circuit does take strain off the Arduino, which should increase longevity and reliability but the bare IO pin did a good job of supplying power. Due to the low cost of the transistors, it seems like a logical choice to keep them in the circuit.
Close-up. The transistor can be seen obscuring the left-most LED
The resistor values used to protect the LEDs on the transistor circuit were a guess at first. After calculating the ideal value brightness increased again and on a whim, a short was created for no resistance aside from the transistor. This dramatically increased the brightness.
Changing from 66Ω to 0Ω
Downloads:
- Arduino firmware
- OpenSCAD code
- STL printable models
- STL printable pipe dividers
- Python Last-Man-Standing program
The rest of the posts for this project have been arranged by date
First time here?
Completed projects from year 1
Completed projects from year 2
Completed projects from year 3
Disclaimer for http://24hourengineer.blogspot.com/ and 24hourengineer.com
This disclaimer must be intact and whole. This disclaimer must be included if a project is distributed.
All information in this blog, or linked by this blog, are not to be taken as advice or solicitation. Anyone attempting to replicate, in whole or in part, is responsible for the outcome and procedure. Any loss of functionality, money, property or similar, is the responsibility of those involved in the replication.
All digital communication regarding the email address 24hourengineer@gmail.com becomes the intellectual property of Brian McEvoy. Any information contained within these messages may be distributed or retained at the discretion of Brian McEvoy. Any email sent to this address, or any email account owned by Brian McEvoy, cannot be used to claim property or assets.
Comments to the blog may be utilized or erased at the discretion of the owner. No one posting may claim property or assets based on a post.
This blog, including pictures and text, is copyright to Brian McEvoy.
2017-05-01 (M)
Comments
Post a Comment