Help a newbie with a question on very small AC motor

Thread Starter

Boytoreckonwith

Joined Dec 15, 2017
6
So, I'm nervous to just experiment with this because it was my wife's (passed) grandma's. While she admits it was a cheap trinket, it means a lot to her. It was an optical flower. It had a AC bulb and AC motor that had a step down transformer. The bulb blew and I couldn't fine a replacement so I bought an LED bulb and LED driver. The problem is that the original bulb was in series, but I had to wire the LED driver pre-transformer. Obviously there is nothing to add resistance to the motor side, which now goes 2 or 3 times faster than it used to. SO THE QUESTION IS.... Do I just need to add resistance in series to the motor (and if so what type/Ohm would you recommend) to slow the motor back down? I'm in over my head. Any ideas?

Please excuse the crude wiring job.
 

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LesJones

Joined Jan 8, 2017
2,525
Do you know the rating of the of the original bulb. (Voltage, wattage, current) Do you have a picture of the original bulb. The LED bulb in your picture looks like it is about the same size as a MR16 halogen bulb. These are normally 12 volts and come in 20, 35 and 50 wattratings. Have you measured the secondary voltage ofthe transformer ?

Les.
 

Thread Starter

Boytoreckonwith

Joined Dec 15, 2017
6
Do you know the rating of the of the original bulb. (Voltage, wattage, current) Do you have a picture of the original bulb. The LED bulb in your picture looks like it is about the same size as a MR16 halogen bulb. These are normally 12 volts and come in 20, 35 and 50 wattratings. Have you measured the secondary voltage ofthe transformer ?

Les.
The original bulb is long gone, but it had no markings. It was getting 12v off the transformer.
 

LesJones

Joined Jan 8, 2017
2,525
I think the trial and error method is going to be the quickest method as you cannot provide any information to estimate a suitable value for the seriies resistance. I would suggest starting with about 47 ohms and adjust up or down untill you get the correct speed.

Les.
 

MaxHeadRoom

Joined Jul 18, 2013
20,063
If it is a AC motor then not much use reading the motor resistance, you would need to read the mean running current to calculate a resistor.
Max.
 

LesJones

Joined Jan 8, 2017
2,525
You are not being very helpful. I have seen screw type bulbs from LES size (5.1mm Dia.) up to one about 45mm on a large projector lamp.

Les.
 

Thread Starter

Boytoreckonwith

Joined Dec 15, 2017
6
Finding the correct bulb would be the easiest thing to get this back up and running. Does the item have a manufactures name and model number?

A sample list of miniature base screw type bulbs, called an E10 base.
https://www.bulbs.com/Light_Bulbs/Miniature_Screw_(E10)-Bulb_Base/results.aspx
Okay, so I actually hadn't thought of replacing the bulb and rewiring it to original. I switched to LED/Driver because all I could find was bulbs rated for DC. Can I use a 12v DC bulb on the AC?
 
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