Invention of the day:  The DC Transformer - Page 1
Forum section: electronics / general

author: RoGeorge
author_rank: Super Contributor
timestamp: September 29, 2024, 01:31:25 pm
content: Tadaaamm!!! Proudly announcing today the mirabulous invention of the DC Transformer!!!Made out of interleaved primary/secondary Peltier elements (TEC).One primary Peltier stacked with one secondary Peltier and so on, such that they alternate hot/cold surfaces, all in thermal contact.Pros:- No mains ripple, so switching power supply noises, no singing coils or capacitors, all quiet, linear and analog, no RF noises- Can raise the DC input voltage entirely passive, by connecting the primary side elements in parallel and the secondary side elements in series- The Peltier elements can be connected in series/parallel, can supply negative DC, multiple isolated secondaries, etc.- The DC transforming ratio can be changed by rewiring the series/parallel connection of the Peltier elements- Eventually can transfer RF signals, too, to bidirectionally transfer data between the primary and the secondary sides of the DC transformer, for example when the DC transformer is used to power a galvanically DC isolated/floating/HV sensor- Same DC transformer may also be used without any DC power, as a thermal energy harvesting device- Smooth powering up response (might be either a pro or a con feature)- The Peltier elements doesn't necessarily need to be interleaved 1 to 1Cons:- Transforming ratio might vary with temperature and/or with the loading- Power efficiency is very bad, might not matter for applications where only mW/uW/nW transfer is needed- Mostly for low power transfers, but it might withstand more power transfer if external radiators are added to extract the extra heat- Might require hydro-isolation against water condensation at the cold areas- Might require radiator fins to evacuate the heat excess

author: Shay
author_rank: Regular Contributor
timestamp: September 29, 2024, 01:35:44 pm
content: Cool (no pun intended)But I think a powerful LED and a small solar panel/photodiode is better? You can even linearize the LED with some negative feedback

author: RoGeorge
author_rank: Super Contributor
timestamp: September 29, 2024, 04:17:28 pm
content: The funny thing is, in theory a normal transformer can pass DC, too. The following is a simulation showing a normal transformer when suddenly powered with DC in the primary. Note how in the last plot the V(out) in the secondary is practically a constant DC voltage for minutes, though the required components values will be highly impractical.LTspice simulation fromhttps://www.eevblog.com/forum/beginners/can-you-pass-dc-through-a-transformer-together-with-0-resistance/msg4955077/#msg4955077

author: Phil1977
author_rank: Frequent Contributor
timestamp: September 29, 2024, 04:48:21 pm
content: Quote from: Shay on September 29, 2024, 01:35:44 pmNitpicking: Light is just very high frequency AC...

author: julian1
author_rank: Frequent Contributor
timestamp: September 29, 2024, 08:24:54 pm
content: How much does stacking raise the efficiency?

author: TimFox
author_rank: Super Contributor
timestamp: September 29, 2024, 08:36:11 pm
content: In my experience with Peltier devices to cool temperature-sensitive circuits, the main engineering problem is removing the waste heat at the hot end.Cooling Peltiers use more electrical power than what they transfer, and both the transferred and electrical power must go out the heat sink.As the temperature of the heat sink increases, the efficiency goes down.(They do work: this is just the main engineering problem for many applications.)

author: julian1
author_rank: Frequent Contributor
timestamp: September 29, 2024, 09:04:15 pm
content: Perhaps they could stack/interleave as a toroid assembly (just like a AC transformer) to reduce -area that creates the dissipation/losses at the side-ends.eg. with heat conductive wedges to close the arc. half serious.

author: Smokey
author_rank: Super Contributor
timestamp: September 29, 2024, 09:13:33 pm
content: Hmmm . If you had an application that ran underwater or something, I bet you could get a fair bit of power output.

author: Benta
author_rank: Super Contributor
timestamp: September 29, 2024, 09:29:12 pm
content: Perhaps if you stacked Peltier- and Seebeck elements*, you might get up to 1% efficiency?*: yes, they're almost the same, but optimized differently.

author: porter
author_rank: Regular Contributor
timestamp: September 29, 2024, 09:31:17 pm
content: Quote from: RoGeorge on September 29, 2024, 04:17:28 pmkudos to Michael Faraday in 1831"Have an iron ring made, iron round and 7/8 inches thick and the ring 6 inches in external diameter. Wound many coils of copperwire round one half, the coils being separated by twine and calico. There were 3 lengths of wire each about 24feet long and they could be connected as one length or used as separate lengths .... Will call this side ofthe ring A. On the other side but separated by an interval was wound wire in two pieces together amounting to about 60 feet inlength, the direction being as with the former coils; this side call B ...Connected the ends of one of the pieces on A side with battery; immediately a sensible effect on theneedle. It oscillated and settled at last in original position.."

author: Kim Christensen
author_rank: Super Contributor
timestamp: September 30, 2024, 12:32:54 am
content: Hmmm... A resistive element on one side of a peltier (Or thermopile) and a heatsink on the other would convert either AC or DC into DC.(Some RF power meters work on this principle)

author: smaultre
author_rank: Regular Contributor
timestamp: September 30, 2024, 05:47:23 am
content: Two DC motors?There was another trick how to increase DC Voltage on battery powered, vacuum tube radio..

author: 5U4GB
author_rank: Super Contributor
timestamp: September 30, 2024, 07:11:08 am
content: Quote from: Phil1977 on September 29, 2024, 04:48:21 pmIt shouldn't take an Einstein to see that it's a bit more complex than that.

author: 5U4GB
author_rank: Super Contributor
timestamp: September 30, 2024, 07:13:42 am
content: Quote from: smaultre on September 30, 2024, 05:47:23 amYeah, I think a DC-only rotary converter would be quite a bit more efficient. However it doesn't have the coolness factor of this setup :-).

author: Phil1977
author_rank: Frequent Contributor
timestamp: September 30, 2024, 07:25:09 am
content: And a DC rotary converter would create lots of noise with its brushing.This could be one of the few real low-noise galvanic isolators for DC...

author: magic
author_rank: Super Contributor
timestamp: September 30, 2024, 07:47:44 am
content: Not sure if there are any motors which produce ready to use smooth DC when used as a generator?Quote from: Shay on September 29, 2024, 01:35:44 pmActually, does anyone know what sort of solar cell(s) it would take to get 0.5~1mA at a volt or two from an LED?

author: Siwastaja
author_rank: Super Contributor
timestamp: September 30, 2024, 08:02:44 am
content: Quote from: Phil1977 on September 30, 2024, 07:25:09 amSo let's do a brushless design - the typical semiconductor design driving the coils. Oh wait, now we can remove the mechanical coupling and just put the motor windings on the same magnetic core. We are getting there!

author: 5U4GB
author_rank: Super Contributor
timestamp: September 30, 2024, 08:19:34 am
content: Quote from: Phil1977 on September 30, 2024, 07:25:09 amYou could go the steampunk way and use the DC input to heat a boiler for closed-loop steam generation. The traditional turbine as generator is going to be quite noisy, but there's all sorts of other ways to run a prime mover with steam.

author: Phil1977
author_rank: Frequent Contributor
timestamp: September 30, 2024, 08:26:54 am
content: But indeed there are not many ways to convert a rotation to DC without using any switches, diodes or sliding contacts.

author: Smokey
author_rank: Super Contributor
timestamp: September 30, 2024, 08:44:24 am
content: Quote from: Phil1977 on September 30, 2024, 08:26:54 amuse the motor to drive a peltier junction! Then hook that peltier up to another peltier then up to another motor!

author: ArdWar
author_rank: Frequent Contributor
timestamp: September 30, 2024, 09:03:59 am
content: Use the motor to drive a refrigeration cycle compressor. If you're lucky you may even get the whole peltier system "efficiency" to "double".

author: tom66
author_rank: Super Contributor
timestamp: September 30, 2024, 10:00:47 am
content: This is all silly. Just use a DC antenna.(Patent pending)

author: tszaboo
author_rank: Super Contributor
timestamp: September 30, 2024, 01:09:27 pm
content: Neat idea. If electricity requires changing magnetic field in a transformer, and DC doesn't have that, then let's go ahead and use a different phenomenon to generate electricity.Quote from: Phil1977 on September 29, 2024, 04:48:21 pmGood question, if LEDs are just small antennas that transmit radio waves on the frequency of light, than where is the oscillator?

author: tom66
author_rank: Super Contributor
timestamp: September 30, 2024, 01:11:12 pm
content: Quote from: tszaboo on September 30, 2024, 01:09:27 pmElectrons precisely falling through the band-gap in the semiconductor material, each producing a photon as they do so?

author: coppice
author_rank: Super Contributor
timestamp: September 30, 2024, 01:29:26 pm
content: The first use we made of the low power benefits of CMOS was to power an 1802 MPU and supporting circuitry monitoring something at 55kV, powered from a photosensor attached to an optical fibre. A second fibre passed back the data stream of the results of the monitoring. I think the other end of the power fibre used a conventional lamp. This was in the late 70s, and LEDs were not that bright back then.

author: tszaboo
author_rank: Super Contributor
timestamp: September 30, 2024, 01:55:11 pm
content: Quote from: tom66 on September 30, 2024, 01:11:12 pmEveryone knows that light is actually waves and photons is just an a way to explain the Bruguière abstraction.

author: 5U4GB
author_rank: Super Contributor
timestamp: October 02, 2024, 08:29:49 am
content: Quote from: Smokey on September 30, 2024, 08:44:24 amThis is starting to sound like the saga of thewind-powered boat from the Red Green Show.