Looking for miniature low power DC to AC converter

[en2oh]

Hi folks,

I'm looking for a surface mount 3 volt DC to 3 volt AC Converter.
Ultimately, I'd like to power a small coil. I need to generate a small AC magnetic field.

Anyone know of a single chip/SMD board capable of doing this? The smaller, the better.

Thanks
Nitrous

 

[ronsimpson]

What current?
What frequency?

You might look at DC motor drivers.

 

[Ian Rogers]

Back light invertors for CCFL can produce a small current at 220vac.. The one's we use produce 110vac for our CCFL 4x20 LCD screens...


There are IC's similar to this.. https://www.electro-tech-online.com/custompdfs/2013/02/UBA2071_A.pdf

 

[en2oh]

Thanks for the reply.
Actually, the purpose is to inductively drive a small stepper motor.
Not sure what the link to DC motor drivers would be. Can you clarify?
Nitrous

 

[en2oh]

Would prefer much lower voltage with somewhat higher current since the lied strength will be amp-turns based.

Thanks
Nitrous

 

[ronv]

Maybe a spec sheet on your motor and how you plan to drive it.

 

[en2oh]

Difficult to get spec sheet as the motor is in a quartz watch movement.

 

[Ian Rogers]

Sorry... Miles out with my suggestion.... Little brushless motors have a little dc-ac converter of that type.. A tiny astable circiut....

 

[en2oh]

Good to know. Would they handle the load of a coil?
This might be exactly what I need.
Is this common to all brushless DC motors?
Nitrous

 

[en2oh]

I've seen single phase IC modules to drive micro brushless motors.
Do these modules output an AC to the motor?
Nitrous

 

[Ian Rogers]

I think so, at least the ones in computer cases... I pulled one apart... it was a bios fan... The set up was just two transistors and two caps..

If you need to do this you might have to use a larger voltage to get you 3vac.. Have you tried the output of a 555 timer set for 60hz, to see if it works.

 

[en2oh]

I think so, at least the ones in computer cases... I pulled one apart... it was a bios fan... The set up was just two transistors and two caps..

If you need to do this you might have to use a larger voltage to get you 3vac.. Have you tried the output of a 555 timer set for 60hz, to see if it works.

I'm trying to generate a "rotating magnetic field". This may be a silly question, but a 555 timer won't generate a +3 to -3 volt "alternating current", will it?

The end result is a circuit that will inductively drive a stepper motor.

Nitrous

 

[dougy83]

I'm trying to generate a "rotating magnetic field". This may be a silly question, but a 555 timer won't generate a +3 to -3 volt "alternating current", will it?

You can use a second 555 as an inverter to get the +/- 3V across the coil. Or you can just put a capacitor in series with the output of a single 555 which can give you pulses of +/- 3V.

You might want to check the frequency required, it's more likely ~1Hz.

 

[MikeMl]

I have designed an IC chip for a watch circuit. The motors in watches are two coil stepping motors. The coils are powered intermittently only while the motor rotor is being positioned to the next step. It is a four phase drive sequence; +coil 1-, +coil2-, -coil1+, -coil2+, repeat. Each coil is driven with an H-bridge. The duty cycle of the current drive is very low to make the battery last as long as possible.

 

[en2oh]

The frequency is much greater than 1pps. I'm not interested in driving the stepper at the normal rate. The goal is to drive it at four times the rate.

Th capacitor idea sounds interesting. Too bad there isn't a simple SMD module that might fit the bill.

Nitrous.

 

[en2oh]

I have designed an IC chip for a watch circuit. The motors in watches are two coil stepping motors. The coils are powered intermittently only while the motor rotor is being positioned to the next step. It is a four phase drive sequence; +coil 1-, +coil2-, -coil1+, -coil2+, repeat. Each coil is driven with an H-bridge. The duty cycle of the current drive is very low to make the battery last as long as possible.

Thanks, this is quite helpful but I'm looking to magnetically drive the stepper motor with a coil applied externally.
This is a common way to both test quartz movements and "condition" the mechanical works that have become gummed up with dried oil.

Thank
Doug

 

[en2oh]

I have designed an IC chip for a watch circuit. The motors in watches are two coil stepping motors. The coils are powered intermittently only while the motor rotor is being positioned to the next step. It is a four phase drive sequence; +coil 1-, +coil2-, -coil1+, -coil2+, repeat. Each coil is driven with an H-bridge. The duty cycle of the current drive is very low to make the battery last as long as possible.

I'm looking at some cheaper quarts movements. They seem to have only one coil. I wonder if the better movements are as you described?

Nitrous

 

[MrAl]

Hi,

Normally you use two H bridges to drive the two coils, as MikeMI said you drive the coils independently. The coils inside are usually 90 degrees apart however, so it may be possible to drive the motor (depends on the motor too) simply with two waves that are 90 degrees out of phase. For example, a sine and cosine wave, the sine applied to one coil and the cosine applied to the other coil. This would provide a smooth action, but if you dont need that then maybe just drive them with two square waves 90 degrees out of phase. Since it is light current, maybe you can use a set of 555's or something like that. A little experimentation will help too.

 

[en2oh]

I have designed an IC chip for a watch circuit. The motors in watches are two coil stepping motors. The coils are powered intermittently only while the motor rotor is being positioned to the next step. It is a four phase drive sequence; +coil 1-, +coil2-, -coil1+, -coil2+, repeat. Each coil is driven with an H-bridge. The duty cycle of the current drive is very low to make the battery last as long as possible.

This link is to a representative single coil stepper driver. I suspect, as some as previously said, that a capacitor or similar circuit (2nd 555) provides the negative pulse.

http://www.mridout.force9.co.uk/ecw/quartzmodern.htm

Nitrous