Convert 110vac LED bulbs to 24vdc?

openplanetopenplanet Registered Users Posts: 34 ✭✭
As most of-gridders know, 110vac LED bulbs are considerably less expensive than decent-quality 12- or 24dc LED bulbs.
Given that the electronics in a 110vac bulb converting the mains voltage back to dc, I'm wondering if anyone has experimented with bypassing\modifying this circuitry in order to make such bulbs usable in lower-voltage dc systems. Shouldn't this be feasible?
Thanks

Comments

  • mike95490mike95490 Solar Expert Posts: 9,571 ✭✭✭✭✭
    Re: Convert 110vac LED bulbs to 24vdc?

    If you understand how to source current to LED's and want to re-engineer a whole new driver, sure. But there are some decent 12V LED/driver packages:
    https://www.wiredco.com/10_LED_SMT_SMD_Warm_White_G4_Disc_LED_Module_12VAC_p/10ledwarmwhiteled.htm
    160 lumens, 2.2w, 12V AC/DC or 8-30V for less than $7
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • openplanetopenplanet Registered Users Posts: 34 ✭✭
    Re: Convert 110vac LED bulbs to 24vdc?

    Thanks very much for the suggestion! I will order a couple and experiment, perhaps putting two in series for use with 24vdc.

    mike95490 wrote: »
    If you understand how to source current to LED's and want to re-engineer a whole new driver, sure. But there are some decent 12V LED/driver packages:
    https://www.wiredco.com/10_LED_SMT_SMD_Warm_White_G4_Disc_LED_Module_12VAC_p/10ledwarmwhiteled.htm
    160 lumens, 2.2w, 12V AC/DC or 8-30V for less than $7
  • BB.BB. Super Moderators, Administrators Posts: 32,608 admin
    Re: Convert 110vac LED bulbs to 24vdc?

    Remember that CFL and LED lamps need special driver circuits called "ballasts".

    A CFL is actually a form or "arc lamp"... It takes (relatively high) voltage to start the "arc", then the resistance drops a lot--And the ballast is to keep constant current going to the lamp. If you just feed DC current to the bulb, it will basically short circuit once the arc starts and something will blow (wiring, internal components of bulb, etc.). CFL's may also require AC power for long life... Many things when feed DC will "plate" materials from one electrode to the other--And quickly blacken/ruin one of the electrodes. AC current does moves a tiny amount of metal ions back and forth--So do not erode electrodes over time (guess on my part).

    LED's also require a ballast. The IV (current voltage) curve of an LED is non-linear and current is very sensitive to voltage (as well as temperature dependent). Put 6.0 volts on an LED--works OK. put 6.2 volts on an LED, excessive current, over heats, dies. Similar 70F at 6.0 volts, current OK. LED die heats to 120 volts, "resistance drops, more current, runs hotter, thermal runaway, dies.

    LEDs either use a resistor to "ballast" (not very efficient), or a capacitor (such as Christmas tree lights on 120 VAC @ 60 Hz), or an actual switch mode DC power supply that will output a specific level of current to drive the LED (sometimes with thermal feedback to limit heat/current).

    For DYI projects, you can go here and find lots of information and even suppliers of ballast and ballast kits/circuits for your projects:

    http://www.candlepowerforums.com/vb/forum.php

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Convert 110vac LED bulbs to 24vdc?
    openplanet wrote: »
    I will order a couple and experiment, perhaps putting two in series for use with 24vdc.

    Research! not everything can be put in series. For example, putting two 12 volt fans in series doesn't work. I really don't know what will happen with LEDs... it may depend upon the drivers.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BB.BB. Super Moderators, Administrators Posts: 32,608 admin
    Re: Convert 110vac LED bulbs to 24vdc?

    You can put a single ballast in series with multiple LEDs--Assuming you meet the specifications for current/voltage/power dissipation. LEDs are, mostly, driven based on specified current. Voltage is allowed to "float" behind the current ballast.

    Of course, you need to make sure that your LED die are well heat sinked. The "old fashion" Txx cased white LEDs were typically overdriven to get lots of (cheaper) light from them. The only heat dissappation was via the lead frames (and that was not much). Inside of 100-500 hours, most of them turned black (phosphors+plastic overheated by LED).

    The high quality LEDs that are larger than a fraction of a watt have heavy metal frames that are mounted to good sized heat sinks. Heat is the enemy of LEDs (and electronics in general).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Convert 110vac LED bulbs to 24vdc?
    BB. wrote: »
    You can put a single ballast in series with multiple LEDs

    :confused: But what if you have two 12 volt LEDs lightbulbs each with its own ballast... can they be put in series on a 24 volt circuit? --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BB.BB. Super Moderators, Administrators Posts: 32,608 admin
    Re: Convert 110vac LED bulbs to 24vdc?
    vtmaps wrote: »
    :confused: But what if you have two 12 volt LEDs lightbulbs each with its own ballast... can they be put in series on a 24 volt circuit? --vtMaps

    It depends...

    If they are resistor or (capacitor if 24 VAC) ballasts--should be fine.

    If they are active (electronic ballasts)--Probably not. Active ballasts are usually "constant current" output devices... And will probably exhibit "negative resistance" on the input that is seen with constant power devices (p=v*i, if v falls, i increases--exactly what you see with AC inverters on their DC input). In a constant output current device (that is a power converter), if input voltage falls, to maintain constant current, the input current will increase causing the input voltage to fall even more). So you have an unstable feed back loop (positive feed back). You might get blinking lights or even an over voltage on the ballast input (if two 12 volt ballasts are in series with their LEDs... One ballasts collapses its voltage, the other sees over rated input voltage).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,571 ✭✭✭✭✭
    Re: Convert 110vac LED bulbs to 24vdc?
    openplanet wrote: »
    .... perhaps putting two in series for use with 24vdc.

    Rated up to 30V maybe contact Wired and see how well they fare @ 24V (and your solar charge voltage of 29V).
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • john pjohn p Solar Expert Posts: 814 ✭✭✭
    Re: Convert 110vac LED bulbs to 24vdc?
    vtmaps wrote: »
    Research! not everything can be put in series. For example, putting two 12 volt fans in series doesn't work. I really don't know what will happen with LEDs... it may depend upon the drivers.

    --vtMaps

    I think someone gave you bad info about the 2x 12v fans. As have done built over 200 amplifiers during the last 20yrs doing that and no complaints from customers saying the amps are overheating due to fan failure.!!!!!!
  • BB.BB. Super Moderators, Administrators Posts: 32,608 admin
    Re: Convert 110vac LED bulbs to 24vdc?

    Fans are "negative feedback"--Lower voltage, and they draw less current/energy--Much different than a compressor which draws more current as the voltage drops.

    So, I could see fans running in series (still could be an issue with maximum voltage and the electronics--Does not take very much time to toast the FETs for electronically commutated fans).

    -Bill

    Guess I should ask if these are two 12 volt fans in series on a 12 volt power supply, or on a 24 volt power supply...
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Convert 110vac LED bulbs to 24vdc?
    john p wrote: »
    I think someone gave you bad info about the 2x 12v fans. As have done built over 200 amplifiers during the last 20yrs doing that and no complaints from customers saying the amps are overheating due to fan failure.!!!!!!
    BB. wrote: »
    Fans are "negative feedback"--Lower voltage, and they draw less current/energy--Much different than a compressor which draws more current as the voltage drops.

    :confused: OK, maybe I'm confused again. I thought that at a given voltage, if a fan stalls it draws more current because its resistance/impedance goes down (as in locked rotor amps)... Am I wrong about that?

    If I am correct, when a fan (in series with another fan) slows down and has lower resistance, it will have lower voltage across it, and the other fan will have the higher voltage. Thus one fan spins faster and the other spins slower.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BB.BB. Super Moderators, Administrators Posts: 32,608 admin
    Re: Convert 110vac LED bulbs to 24vdc?

    In general, the slower the fan turns, the less torque needed to turn the blades (rpm*torque=power).

    For compressors, the torque is relatively constant, regardless of speed--So the lower the voltage, the higher the current needed to keep up with the torque).

    Of course, there are differences between Induction motors (more or less fixed line frequency, so lower voltage * more current to keep constant power because of constant RPM and Torque--Brownouts of AC utility power will smoke compressor motors).

    With electronically comutated motors (brush-less DC), it depends on the control circuitry... For DC computer fans, they seem to drop the RPM as the input voltage falls--So, that would reduce both RPM and Torque, reducing power and current.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • john pjohn p Solar Expert Posts: 814 ✭✭✭
    Re: Convert 110vac LED bulbs to 24vdc?

    To be honest have never checked if the speed of both fans is identical.. All I can say is visually they look like there doing the same RPM,
    It seems to make no difference if you connect 2 x12v fans in series across 12v or 24v . except for RPM of course.. And it makes no difference if the fans are not identical.. ie. 1x 80mm 1x60mm.

    We used them in series in amplifiers to simplify supply from a 50v rail.
    Now we use 240v fans with magnetic levitation and as no possible bearing wear and very low noise they run all the time amp is on.. We were unable to get approved 240v AC thermal switches way back then. And leaving ball or sleeve bearing fans on all the time soon wears them out. regardless of what manufacturers say.
    Actually I have never bothered to understand how they worked or not as long as they did.
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Convert 110vac LED bulbs to 24vdc?
    BB. wrote: »
    In general, the slower the fan turns, the less torque needed to turn the blades (rpm*torque=power).

    In that equation, the power is the OUTPUT power of the fan, isn't it? If it were the input power the fan couldn't start from zero rpm because it would draw no power (zero * torque = zero).
    BB. wrote: »
    For DC computer fans, they seem to drop the RPM as the input voltage falls--So, that would reduce both RPM and Torque, reducing power and current.

    I haven't tried this (maybe 'john p' has), but if I understand what you are writing... if two of these computer fans are in series if I stop one (hold the blades fixed) the other should also stop because they have the same current.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • john pjohn p Solar Expert Posts: 814 ✭✭✭
    Re: Convert 110vac LED bulbs to 24vdc?

    VTMAPS out of curiosity just tried it. if you hold the blades of one to stop rotation the other one just keeps going.
  • john pjohn p Solar Expert Posts: 814 ✭✭✭
    Re: Convert 110vac LED bulbs to 24vdc?

    This has been interesting subject as previously never gave it any thought and never even considered that two fans in series would not work because they did. I never gave thought at all to the electrical reasons as had no need to do so.. Mabe if it had not worked would have delved into the reasons..
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Convert 110vac LED bulbs to 24vdc?
    john p wrote: »
    VTMAPS out of curiosity just tried it. if you hold the blades of one to stop rotation the other one just keeps going.

    Thanks for the report... What you are saying, in effect, is that when you stop one of the two fans (in series) the voltage across and the current through that fan are unchanged. I guess I need to learn more about these DC brushless motors work.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
Sign In or Register to comment.