Recently I was out looking for a variable DC power supply.
Something that would give a power output in the range of 1.5 - 12volts would be ideal.
While searching around I spotted on ebay a number of potential candidates. Surprisingly they are being sold as 'Tatoo Power Supplies'. Some very economical ones can be found for as little as $15 - $20.
I quickly purchased a suitable looking candidate.
On receiving the supply I was initially struggling to get anything out of it.
As can be seen from the picture - the unit had three audio style jacks on the front, and 1 switch. These where labeled.
LEFT | RIGHT | FOOT
Having no documentation to hand I whipped open the case and started to trace the circuit on the board.
In the end the fix was really easy. In the 'Tatoo' world they no doubt use a foot pedal to turn power on & off. The socket labeled as 'FOOT' no doubt was designed to have some sort of switch attached to it.
I solved the issue by simply removing the audio socket and hard wiring a jumper across the polls.
You can see on the inside shot above where the blue jumper bridges the pins.
Not content at this point I then modified the 'lead' that they provided as standard. The stock system had a rather odd adapter on the end that I can only assume is known in the Tatoo World!
I simply took that off and wired in two rather more useful leads. (JST & Servo)
Tests with the supply using a meter have shown the onboard display to be accurate to within 0.1 of a volt.
All up.. I am happy with the unit. It is cheap - simple - and saved me spending more than $100 on an 'electronic stores' one!
Rob
Cheap Variable Power Supply
- Rob Thomson
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Cheap Variable Power Supply
Slope Soaring, FPV, and pretty much anything 'high tech'
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Re: Cheap Variable Power Supply
Nice find!
This is a must for electronic tinkerers... I splurged and bought a digital PS but for the low AMP stuff that I need this could have been just as good.
You might consider adding a couple of capacitors on the output to reduce ripple and make it really good!
This is a must for electronic tinkerers... I splurged and bought a digital PS but for the low AMP stuff that I need this could have been just as good.
You might consider adding a couple of capacitors on the output to reduce ripple and make it really good!
Z
BEWARE - WE ARE IN THE AIR!!!
What goes up... Should be controlled by a 9X!
BEWARE - WE ARE IN THE AIR!!!
What goes up... Should be controlled by a 9X!
- Rob Thomson
- Site Admin
- Posts: 4543
- Joined: Tue Dec 27, 2011 11:34 am
- Country: United Kingdom
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Re: Cheap Variable Power Supply
Good idea! Any thoughts on the size?
Slope Soaring, FPV, and pretty much anything 'high tech'
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!
...........if you think it should be in the wiki.. ask me for wiki access, then go add it!
Re: Cheap Variable Power Supply
Do not put a large caps on a regulator output , put them on the input.
From the picture it uses a 3 terminal LM317 regulator.
Linear regulators do not like large capactive loads , it can cause the voltage on the output of the regulator to be larger
than the voltage on the input to the regulator when the power is switched off , this can cause a failure in the Regulator.
A larger cap on the input side of the regulator will help a bit.
A cap in the range of 2200uf /25V would work well on the input side of the regulator.
-Brent
From the picture it uses a 3 terminal LM317 regulator.
Linear regulators do not like large capactive loads , it can cause the voltage on the output of the regulator to be larger
than the voltage on the input to the regulator when the power is switched off , this can cause a failure in the Regulator.
A larger cap on the input side of the regulator will help a bit.
A cap in the range of 2200uf /25V would work well on the input side of the regulator.
-Brent
Re: Cheap Variable Power Supply
Which is why when I am putting together a linear regulator PSU, that I fit a diode across the input and output pins of the regulator (diode anode to the output pin on positive regulators) to prevent that from happening. That is in addition to a crowbar circuit in case the regulator should go short circuit, but that is another story.SkyNorth wrote:Linear regulators do not like large capactive loads , it can cause the voltage on the output of the regulator to be larger
than the voltage on the input to the regulator when the power is switched off , this can cause a failure in the Regulator.