Need a powersupply built for me.

[Anonymous]

I am in need of a powersupply that takes household current and transforms it into 74vdc to run a Gyralite I picked up recently. I also have a Prime digital beacon that I could run as well. The Gyralite draws the most power of the two with its light bulb and motor. Anybody able to help or know someone that could build this up for me. Thanks Mike

[chad thomas]

You would be better off going with batteries. Power supplies that can provide this odd voltage are quite spendy.

If you buy one be prepared to spend a couple hundred bucks.

If you want to build your own it's relativly simple. Just get a 60volt transformer ($$$), a full wave rectifier rated to handle the current ($$$), and a suitable filter (capacitor) (more $$$).

[chad thomas]

Here is a link to mouser electronics power supplys.

http://www.mouser.com/?Ne=601&handler=data.listcategory&N=600

[Anonymous]

I figured they wouldnt be cheap, the motor is mady by RAE, located near chicago and they offer thier motors in lower voltages including 12vdc, so I emailed them to see if I can get a replacement motor that will run on 12 instead of 74 volts, I can use a different sealed beam lamp in that case, the one in the light is a phillips 200wt, 30volt, but the motor is a 74 volt motor, so it came off an older locomotive with 30volt headlights. Cheers Mike

[chad thomas]

Mike,

Converting to 12v is definatly the way to go if you can do it. There is a cheaper (but much more risky) way to run it at 74vdc. You can use a houshold light dimmer (triac controlled) and a big diode. Run it right off of the 110vac wall outlet plug but be very carefull not to excede the max voltage of the unit or you could kill it.
If there is anything I can do let me know.

Good luck
Chad

[Anonymous]

I am somewhat electricaly inclined, I under stand the using the light dimmer part, I have a digital meter so I can set it around 60-65 volts to protect the motor. I assume you would use the diode to make dc out of AC. As I understand it, I would need a bridge rectifier capable of handling the amp draw of the unit. I hopefully will hear back on monday from RAE about a replacement motor, the bulb is a standard par 56 lamp, I think I can get it in a lower voltage.

[chad thomas]

The way the dimmer works is it reduces the duty cycle not nessasarly the voltage. So the best bet is to hook it all up with the dimmer all the way dimmed and bring it up slowly till the unit comes to life like it's suppose to. Like I said it's kinda risky but very cheap. A dimmer costs what around 5-10 bucks. The diode (not a full rectifier) is about the same price. It sure beats the hundreds of dollars you would spend on a power supply.

[Overmod]

Six car batteries in series. 72 volts and 74 volts are functionally indistinguishable. Rig a means of charging in parallel at appropriate voltage (you could charge 'em sequentially with cables and a car alternator, too, if that's easier).

Keep in mind that the rated 'voltage' of the motor may not dictate what voltage you actually have to run the thing at -- permag motors, for example, are frequently 'rated' at the voltage that produces rated speed, with lower voltage producing lower speed rather than higher amps (as would be the case with a fixed-wattage load).

On the other hand, even weird stuff sometimes appears for what "engineers" consider 'good' reason. We had a Collins stereo FM transmitter from the early '60s at our college radio station, 17kW ERP (which translated into just over 10kW at the final stage). One day, the blower burned out. We pulled the unit and found (to our amazement) that somebody had installed a 120V motor on a 230V line... small wonder it burned out! In some indignation we called Collins Radio to complain about this, and to express some amazement that the thing had lasted so long (about 14 years at that point). What they told us was that the motor spec was INTENTIONAL -- the motor ran in the flow of cooling air to the tube, and therefore the excessive heat rise that would have been the result of the overvoltage operation would be safely dissipated shy of the max temperature rating. Of course,as soon as this airflow became obstructed -- filters, crud in the duct, etc. -- the motor would fry... but (you can hear the argument already, can't ya) it would be the user's fault because proper maintenance procedures weren't followed.

These were the same guys that supplied the $63-odd (in 1976 dollars) -- plus $150 for rush overnight delivery in those pre-FedEx days -- "Opto-Isolator Module" that provided a vaunted pure resistance when the mixdown-board potentiometers were adjusted. Anybody care to guess what was inside?

[Anonymous]

There is a site on the web devoted to gyrating warning lights, he states that the 74vdc motors will run OK on 60volts, but with a 30volt bulb, I will wait for a responce from RAE motors on a lower voltage replacement motor. I can come up with a 74v bulb easy enough as the GE locomotive factory is here where I live, I just have to ask for a bulb. Cheers MIke

[adrianspeeder]

I would use some cheap lawn tractor/ motorcycle batteries in series, and just put trickle chargers on em.

Adrianspeeder