Re: [CAD_CAM_EDM_DRO] PCB design and manufacture

On Thu, 15 Apr 2004 20:59:00 -0400, you wrote:

>Alright, I am designing the card right now, but have a newbie question.. How
>well do DC and AC interact?
>I have 25-35x AC motors, and need to control them via the
>parallel/serial/usb port, but I was planning on using some NPN transistors
>as amps, with the base being DC and the amp power being the collector..
>But for some reason I don't think this will work...

In this case, they react very badly.

Transistors are made to switch/control one polarity.

Feed them the wrong polarity (other half of the AC cycle) and they go
poof....

Poof is bad....

If you want to turn them on and off only, then you can use a zero
crossing switch/relay rated for the motor's voltage and current. It's
controlled by an LED kind of input.

If you want to get speed control out of them, and they're the type of
motor that can respond to different voltages by different speeds
(generally not an AC motor, BTW), then you can use a circuit that acts
like a triac speed control. (good way to do this might be a light
dimmer, and replace the pot with an *isolated* photocell/LED
combination, you'll get a speed control out of that, use the really
cheap rotary knob kind.

If the motors are two phase, then you can control them by changing the
phase between the two windings... but this is often exactly what
happens in a stepper...

Harvey

>
>Any ideas?
>
>thanks-lee
>
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>----- Original Message -----
>From: "Ron" <veeguy@...>
>To: <CAD_CAM_EDM_DRO@yahoogroups.com>
>Sent: Thursday, April 15, 2004 12:02 PM
>Subject: [CAD_CAM_EDM_DRO] PCB design and manufacture
>
>
>> >From: Steven Ciciora <sciciora@...>
>> >Subject: Re: Re: Servos and Controller boards (where/how to make
>> >PCBs)
>>
>> I use pcb123.com for my board design.
>>
>> Very nice work, professional industrial quality product, *very* low
>> prices. 1 or 1000 units, your choice.
>>
>> The design software is FREE.
>>
>> And a very nice touch -as you design your board, there is a real
>> time price displayed!
>>
>> You can do several versions of a board to minimise cost, or see what
>> adding an optional component would cost.
>>
>> veeguy
>>
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>OFF Topic POSTS: General Machining
>If you wish to post on unlimited OT subjects goto: aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble.
>http://www.metalworking.com/news_servers.html
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>http://groups.yahoo.com/group/jobshophomeshop I consider this to be a sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list.
>
>NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
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