I recently purchased via Amazon from www.xcsource.com XCSOURCE® 5X New 3.3V 5V Solderless MB102 Breadboard Power Supply Module Adapter For Arduino Breadboard TE107 .
This prompted me to post to Amazon a review:-
*** Value for money, check the 3.3v if you have problems. By Peter D Hull on 20 Mar. 2015
Verified Purchase
Good value for Money.
However, they are clones of the YwRobot board and suffer from sawtooth oscillation on the 3.3v rail under no load if powered up by the on-board switch.
I've not seen this on a genuine YwRobot board (yet). This should in most cases be unimportant, if the rail is loaded or has adequate decoupling it doesn't seem to happen. However be ready for this issue if you have problems with the 3.3v supply.
Please note the Female Socket is an output only, do not feed voltage into this port. On this version if 12v is input to the barrel jack 5v is seen on the USB Female socket exactly as should be expected by the USB standard. I have not seen any signs of oscilation on the 5v rail probably because the 3.3v regulator means that the 5v regulator is never unloaded.
I have used a few of these YwRobot breadboard power supply boards and have found them very useful. They work well on American and far Eastern MB 102 breadboard's. However beware that the UK breadboards sold by people such as Maplin do not have the same distance between the power rails that the standard American and far Eastern breadboards have.
I was interested to note that the breadboard power supply boards that arrived do not seen to be legitimate production from YwRobo. The size of the capacitors used is slightly different, the quality of the printing is slightly poorer and they are missing the part number 545043 that is found on legitimate copies of the board.
This prompted me to spend some time comparing and testing these five new boards against one of my older and believed legitimate boards.
If the power switch on the board is switched on before power is plugged into the barrel jack then I cannot detect any difference between the clone boards and the originals I have measured the output voltages and I have use an oscilloscope to look for ripple or oscillation and none can be found.
If the task switch on the board is switched off before power is plugged into the barrel jack then when the switch is operated a difference becomes very apparent. In my test environment I have the top rails set for five volts and the bottom rails set for 3.3 volts. In this case with an unloaded 3.3 V rail the supply is seen to oscillate superimposing about half a volt of sawtooth wave on top of the 3.3 V output connecting a load such as a 39 ohm resistor to the rail causes the oscillation to cease also when the resistor is remote the output stays clean. However if we turn the switch off and back on again the oscillation reappears immediately.
A lesser load increases the oscillation frequency :-
This is with a 1k ohm resistor if a lower value such as 39 ohms is used the oscilation stops immediately and removing the resistor leaves the supply stable till the power is switched off and back on.
Luckily as can be seen the sawtooth wave causes the voltage to drop rather than exceed the specification.
If a capacitor such as a 4.7uf electrolytic is connected across the power rail to earth then the supply becomes stable and even if the capacitor is removed remains stable until it is powered on again. So some simple output bypass capacitors make the supply board appear to be perfectly stable.
I will try to look at stability under a varying load in a later blog post.
So in summary good value for money but don't forget to smooth the 3.3v rail!
I was interested to note that the breadboard power supply boards that arrived do not seen to be legitimate production from YwRobo. The size of the capacitors used is slightly different, the quality of the printing is slightly poorer and they are missing the part number 545043 that is found on legitimate copies of the board.
This prompted me to spend some time comparing and testing these five new boards against one of my older and believed legitimate boards.
If the power switch on the board is switched on before power is plugged into the barrel jack then I cannot detect any difference between the clone boards and the originals I have measured the output voltages and I have use an oscilloscope to look for ripple or oscillation and none can be found.
If the task switch on the board is switched off before power is plugged into the barrel jack then when the switch is operated a difference becomes very apparent. In my test environment I have the top rails set for five volts and the bottom rails set for 3.3 volts. In this case with an unloaded 3.3 V rail the supply is seen to oscillate superimposing about half a volt of sawtooth wave on top of the 3.3 V output connecting a load such as a 39 ohm resistor to the rail causes the oscillation to cease also when the resistor is remote the output stays clean. However if we turn the switch off and back on again the oscillation reappears immediately.
A lesser load increases the oscillation frequency :-
This is with a 1k ohm resistor if a lower value such as 39 ohms is used the oscilation stops immediately and removing the resistor leaves the supply stable till the power is switched off and back on.
Luckily as can be seen the sawtooth wave causes the voltage to drop rather than exceed the specification.
If a capacitor such as a 4.7uf electrolytic is connected across the power rail to earth then the supply becomes stable and even if the capacitor is removed remains stable until it is powered on again. So some simple output bypass capacitors make the supply board appear to be perfectly stable.
I will try to look at stability under a varying load in a later blog post.
So in summary good value for money but don't forget to smooth the 3.3v rail!
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