How to build a power supply for DDS Function Signal Generator module
After building a DDS function signal generator I found out that, in order to power it on, it requires three different input DC voltages: 12V, -12V and 5V.
Obviously one can find a 12VDC power supply but I really don't want to use different PSU for each of those three voltages. So how to solve this problem?
Well, starting with 12VDC we can step-down and regulate the voltage to 5VDC quite easily. The easiest method is by using a LM7805 voltage regulator. OtherÂ parts required are 2 polarized electrolytic capacitors (to filter the output) as shown in the schematic below:
OK, but how about the -12VDC? Well, this is a little bit more complicated in the sense that we are going to need more components which will result in a more complex circuit than the above. The circuit is based on a 555-timer IC and works as in the simulation below:
The schematics for this circuit (excluding the dummy resistor-LED load as in the animation above) looks like this:
So in order to make this circuit we are going to need the following parts:
- C1=10nF (tantalum)
- C4=22uF (polarized ceramic)
- C5=22nF (tantalum)
- C6=100uF (polarized ceramic)
(*) x=is anything from 1-7
So finally the aggregatedÂ circuit schematics of the power supply for DDS Function Signal Generator (including a 4-pin header) would look like this:
The input 12VDC can be obtained from a 110-220VAC to 12VDC (@1A) power supply that can be bought for less than $2 from eBay.
The -12VDC output is obtained from the pin-2 of the header block.
The 5VDC output is obtained from the pin-3 of the header block.
The PCB board net routes can be arranged like this:
If you are using a perforated board instead of etching the PCB by yourself then perhaps the below board layout might help you. Please note that here I used jumper wires (red/blue) instead of copper traces marked with red/blue lines in the example above. The jumper wires are soldered on the back.
OK, soldering the parts was easy. Soldering the net could be a challenge depending on your soldering skills. The final circuit board could look like this (or better):
Note: due the fact that I don't have a 330nF capacitor I've replaced the capacitor C1 (330nF) in the above circuit with 3 parallel-connected 100nF capacitors. Their total equivalent capacity is the all parallel-connected capacitors, ie. 300nF.
Now, if you think that this article was interesting don't forget to rate it. It shows me that you care and thus I will continue write about these things.
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