Aboutcleggsan Expertise All technical areas of Electronics Engineering.
Experience BSEE, MBA, Design, R&D, University Research.
Senior Life Member of IEEE. Life Fellow of AES.
Organizations IEEE, Consumer Electronics Society, Audio Engineering Society.
Broad teaching experience; work experience mostly in consumer electronics and conversion from analog to digital technologies. Pioneer in digital audio at all levels.
Question QUESTION: The motor speed needs to be variable. A schematic would be much appreciated. IMAGE: schematic
ANSWER: ONE: From the looks of the transformer in your image it may not be sufficient (power) to drive the windshield wiper motor - - depends on how much load you are going to place on it.
TWO: There are a few ways to make it variable speed. One is to add an electronic motor control. Another would be to use a rheostat to the dc output of the inverter.
THREE: Here is schematic and construction of a unit with electronic regulator that will work.
QUESTION: BIG THANK YOU appreciated. I know the watts on the Transformer is 5 and thought that would cover the unknown motor wattage. I am doubtful 2 amps will be enough to power the motor at low speeds but will attempt ordering from Radio Shack unless you may know where I can buy the already put together item in quantity.
Answer You did not say how many "quantity" you are thinking, but for a few hundred to a few thousand you can usually have items like this custom made to your specifications by factories in Hong Kong and China. Manufacturing cost is not so great I think.
Also, there are many inverters and converters of all kinds that are available online.
You need to do some testing to find out what the current requirements are of the motor you are using. The current for a typical windshield used in automotive applications can draw up to 12 amps or more. They also have a built in stall-out for when the wiper blade gets stuck in snow or ice. So, you will need to know more about the motor you have selected and compare it against the application you have in mind. For example, if the load you intend is constant and not changing then the current level can be set. But, if the motor speed is variable and the load is variable you will need to know what the range of speed and load is going to result in from the power supply.
Finally, if the application is toy level that is one thing, but if being used in something more scientific that would be another matter. For toy products, simplicity of design and very high durability is important.
There are many, many commercial products for conversion of 120ac to dc. The above is just one example. Once you know more about the power requirements and the voltage variation you need you can get closer to choosing the product you think will do the job. If a commercial unit is close to what you need you can always contact the manufacturer and get price quotations for quantities. Small manufacturers are often willing to custom design a model for your own specific needs when the quantities are sufficient.
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