Forums

Transformerless power supply

Started by amdx August 10, 2018
Is it reasonable/possible to build an 8 amp 20 V transformerless power 
supply from a 120Vac line.
  I calculate about 180uf plus or minus depending on other components.
  Maybe 9- 20uf caps in parallel?
  I'd like to build it into a leaf blower.
  All plastic, absolutely no metal exposed.

  I think I've answered my question, I have 12, X rated caps in my junk 
box, but they are only 1uf.
The cheapest 20uf I can find is $3, so $27 for 9 caps. Not reasonable.

  Just had another thought, I could mount a power supply with 
transformer on the wall and have a cord go to the leaf blower. Just 
trying to build a light weight Leaf Blower for the wife to clean the 
garage once a week.
Daughter gave me the leaf blower after the battery charger gave up.

  Input encouraged.
                  Mikek
Broom?
On 6/20/2020 9:54 AM, jraffayroux@gmail.com wrote:
> Broom? >
Hey, thanks for the input! Mikek -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus
On 2018-08-10, amdx <nojunk@knology.net> wrote:
> Just > trying to build a light weight Leaf Blower for the wife to clean the > garage once a week.
> Is it reasonable/possible to build an 8 amp 20 V transformerless power > supply from a 120Vac line.
depends what you mean "transformerless"
> I calculate about 180uf plus or minus depending on other components. > Maybe 9- 20uf caps in parallel?
You are nuts! using a capacitive dropper to make 8A is crazy. what is your plan for reinforcing the insulation on the leaf blower? Is this a plot to kill your wife?
> I'd like to build it into a leaf blower. > All plastic, absolutely no metal exposed.
That seems half safe so far.
> I think I've answered my question, I have 12, X rated caps in my junk > box, but they are only 1uf. > The cheapest 20uf I can find is $3, so $27 for 9 caps. Not reasonable. > > Just had another thought, I could mount a power supply with > transformer on the wall and have a cord go to the leaf blower.
That seems more reasonable, regular iron transformers with large rectifiers work well for powering DC motor loads. switching supplies can work too, but they usually need a current limit so that they can survive a stall, it may be possible to attach a switching supoply directly to the blower. I guessing you don't have an air compressor (the type used for air tools, not a mere tyre pumper) in your garage. -- Jasen.
amdx wrote:

-----------
> Is it reasonable/possible to build an 8 amp 20 V transformerless power > supply from a 120Vac line. > I calculate about 180uf plus or minus depending on other components. > Maybe 9- 20uf caps in parallel? > I'd like to build it into a leaf blower. > All plastic, absolutely no metal exposed. >
** With a low resistance load, the inrush surge from a 180uF cap would trip the breaker. SMPS have resistors or NTC thermistors in series with the AC supply stop this. ..... Phil
On 8/10/2018 1:24 PM, amdx wrote:
...
> Daughter gave me the leaf blower after the battery charger gave up.
Fix, build, or buy a battery charger.
On 6/21/2020 3:54 AM, Bob Engelhardt wrote:
> On 8/10/2018 1:24 PM, amdx wrote: > ... >> Daughter gave me the leaf blower after the battery charger gave up. > > Fix, build, or buy a battery charger.
And batteries, just not worth it. -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus
On 6/21/2020 6:53 AM, amdx wrote:
> On 6/21/2020 3:54 AM, Bob Engelhardt wrote: >> On 8/10/2018 1:24 PM, amdx wrote: >> ... >>> Daughter gave me the leaf blower after the battery charger gave up. >> >> Fix, build, or buy a battery charger. > > And batteries, just not worth it. >
Just to put this thread to rest, (it was resurrected after 20 months), I rewound an MOT to have a 22V winding, Then full wave rectified it a to power the Leaf blower. All described in SED under "Rewinding a MOT". Mikek -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus