I am working on a complex project that required me to make a voltage divider. I am documenting the other project very thoroughly as part of a residency at Signal Culture in Owego NY. I thought I would share my process on this sub-system.
There are many reasons you may need a different voltage than the supply provides. You don't want to apply an 'over-voltage' to a device or at times you may need to provide different voltages for different devices within you design. Voltage dividing is method of using resistor and/or capacitors to create fractional voltages to match requirements of your component.
This tutorial will demonstrate the construction of a breakout board that will step down voltage by 5/6's the orginal voltage e.g. 5V to 4.38V.
Step 1: Tools and Supplies
To recreate or modify this project, you will need:
- multimeter ( I got a killer deal on this auto ranging model )
- tape, self locking tweezer (like these) or something to hold parts still on the board
- solder iron
- flush cutting pliers (like these)
- a power supply (this is dependent on your project)
Step 2: A Bit of Information on Voltage Dividing
A typical voltage divider is constructed by putting two resistors in series. The junction of the two has a fractional voltage of the source.
The formula for calculation of the Vout is as follows the product of R2 divided by the sum of R1 and R2 times the value of Vin
Solving algebraic equations is always fun, but we live in the age of the internet. You will find many sites that will help you calculate a value for the unknown factor. Do a quick search for a 'voltage divider calculator' and you should have lots of options. In example this I want to drop 6VDC to 5VDC. I happen to have some 2kΩ (2000Ω) resistors on hand. Because I have 3 of the 4 variables this is a breeze with the online calculator. I used the Raltron site this time.
Using the values for Vin (6V) and Vout (5V). Let's use a value of 2000Ω for R1 we get a result of 10000Ω or as it is regularly called 10kΩ for R2.
All resistor have a tolerance, which means they will be close to the value but they promised to be with an error percentage. I tested the 2k and 10k with my meter and I got 1976 and 9940. When I put 6V in for Vin and these actual resistance values the Vout comes to 5.005VDC which is close enough for my needs.
Step 3: Time to Layout a Board
I am going to use the resistors and to make this board plug-n-play I will use header pins. The great thing about this kind of simple board it is matches the drawing very closely. So I am going layout the materials in a very similar fashion.
Step 4: Adding the Resistors
Lay the resistors out in the same 90 degree fashion as the drawing. Note that I left some room above and to the left for add the components or room to adjust if I make an error. That never happens! NEVER.
I used tape to hold them close to the board in order to solder them well. Another technique you can use is to use a pair of the squeeze to open tweezers (seen in the pics).
TIP: To reduce the chance of a part breaking off your board make it as snug as reasonable.
Trim the excess leads from the resistors but don't toss them yet, I have another tip for you.leadlle
Step 5: Place the Header Pins
I started by placing the ground pins. I used a row of 4 pins, an arbitrary decision, but it is good to have many grounds. I placed them so the long side would face up making it easy to use a jumper. Again you want the base tight against the board. You can use the tweezers, tape, poster tack - anything easy to remove after you get the ends soldered so it stays tight. Look to get fully filled, peaked and shiny solder joints for maximum solder weld.
Next place your in and out pins in the same way. I had a two pin set and a three pin row about so I used those. I would recommend that the minimum to use is 2 pins as it will stabilize the setup and give you a better hold.
Step 6: Tie Together the Pins and Resistors
Now time to bridge all those individual pins together so you can make all the connections.
Remember those leads I had you save? Here's where you use them. It is easier to run the solder across a piece of metal, in fact, the plastic the boar is made of rejects the solder. Because of surface tension sometimes the solder jumps all to one side of the bridge. You end up making a big mess by adding too much solder to compensate.
We will lay the legs down next to the solder joints we made and let it gather the material. Use the clamp before you reheat (aka reflow) the solder. You would want to mess up your good work. You will likely need to add more solder but it should be really quick and a small neat amount.
TIP: Use scrap legs to help bridge connections.
Step 7: Completed Voltage Divider
This device should help transform down any voltage to 5/6's the Vin. The moment of truth. I have a 5VDC power supply I already setup with female jumper ends. When I check the voltage from the supply I got an actual rading of 5.24 or 5.25 VDC. Checking the Raltron site, the calculator says I should get 4.38VDC from the divider. AND IT DOES WOOOOOO.
Thanks for reading.