analog to pwm controller

Discussion in 'General Electronics Chat' started by s900t8v, Apr 15, 2013.

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  1. s900t8v

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    Mar 12, 2011
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    I have an analog voltage 0-5v that I want to come out as pwm with increasing frequency as voltage goes up... is there a chepa and simple product I can buy for this

    thanks :)

    I want to control a 12v solenoid with a pwm
     
    Last edited: Apr 15, 2013
  2. Brownout

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    Jan 10, 2012
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    If you want PWM, then why increasing frequency?
     
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  3. Gibson486

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    Jul 20, 2012
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    Just buy one of the many micro controllers on the market (PIC, Atmel, etc). If you do not want to invest too much into programming, just get an Arduino. Also, since you want to run a 12V solenoid, you will also have to have external electronics (ie a mosfet or bjt) as well.
     
  4. Gibson486

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    Jul 20, 2012
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    I think he means duty cycle.
     
  5. s900t8v

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    Mar 12, 2011
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    yeah I did mean duty cycle lol I am no electronics whizz I must say I really dont know very much at all

    I am trying to get a water solenoid to pulse on and off based on input from a linear voltage (0-5 or 0-10v)
     
  6. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Pretty sure you can do this with a SG3525 chip with no micro controller. It (the sg3525 family of chips) is pretty versatile for many PWM like this. It uses a 0V-5V to control the PWMand it even provides that voltage to control its self. The PWM is adjustable from 5% to 90%, if you can live with that range.

    Add a mosfet and depending on the switching speed a mosfet driver and your good to go.
     
  7. Brownout

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    At what duty cycle will the solenoid turn on?
     
  8. Papabravo

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  9. s900t8v

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    Mar 12, 2011
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    I think I may have misunderstood this whole system.

    I want the solenoid to turn on/off at a lower duty cycle I just want that to occur more slowly than at a higher duty cycle?

    the issue is using a cheap 12v solenoid I dont' think it has teh ability to switch on and off as fast as would make it easy.

    you can't learn this stuff over night apparently lol
     
  10. Brownout

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    Maybe if you told us exactly what you're trying to do, we can offer better help.
     
  11. s900t8v

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    Mar 12, 2011
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    I have a 240V 50hz 50w ulka vibrator motor that I'm using to spray high pressure water out a nozzle. There is an in line water solenoid to allow water to come out when circuit closes

    Because its being run by a 12v battery I am using a cheap inverter to convert the power to 240v. APparently the pump prefers 12v with some modifications but I don't know what they are

    Basically I want to control either the pump speed to vary the flow (it's ac so not sure how) or contrOl how often the solenoid clicks on and off (to vary the flow)

    I want the amount of flow to proPortionsl to the voltage 0-5v liner. With the ability if possible to adjust duty cycle ramp up rate and frequency as well as starting voltage.

    The solenoid is just a standard 1/4" water solenoid. Not sure if it can be used in a fast switching system although I know there at super fast switching units in existence.

    Varying the ac pump could be easier but I don't know if you can? Lol
     
  12. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    I have very little experience with solenoids, but I don't really see why one would use PWM on a solenoid. Isn't a solenoid just an electromagnet that pushes or pulls a plunger? In other words, isn't it an ON or OFF device? What am I missing?
     
    Last edited: Apr 15, 2013
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  13. GopherT

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    Nov 23, 2012
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    See post #8 where the OP realizes he didn't mean PWM.
     
  14. tracecom

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    Apr 16, 2010
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    OK, after some Googling, I am guessing that the OP has this vibrator pump from a coffee maker that runs on 220VAC and a water solenoid that runs on 12VDC. He wants to vary the amount of water that is pumped in proportion to a 0-5VDC signal.

    Apparently, the solenoid has to have pressure on its input in order to function, which means the solenoid has to be on the outlet of the pump. If the pump motor has an automatic shutoff (which I don't know), then the solenoid could be operated and released to control the amount of water. Of course, the operation and release could not be in the milliseconds range without wearing the solenoid and the pump motor out in short order.

    If all my speculation is correct (unlikely), then it might be possible to control the solenoid valve, and thereby control the water flow. Of course, that would mean that the output from the solenoid would be a series of spurts of variable duration. If the on/off cycle was very fast, then the life of the solenoid and the pump motor would be reduced.

    If the pump speed must be varied, given that the pump motor is AC, this would mean a circuit involving mains voltage, which is probably not a good idea for an inexperienced tinkerer.

    If the OP cares to state what it is that he/she is trying to accomplish, there may be a way to proceed, but absent that information, I don't have any suggestion (except maybe to buy a 12VDC espresso machine.)
     
    Last edited: Apr 15, 2013
  15. Lundwall_Paul

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    Oct 18, 2011
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    When I think of PWM's I think of width (duty cycle)
     
  16. GopherT

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    Nov 23, 2012
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    Yes, that has been taken care of already, See post number 5
     
  17. s900t8v

    Thread Starter Member

    Mar 12, 2011
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    Hi all thanks for your interest, sorry for being what must be annoyingly vague I forget how helpful context is lol ! :)

    For a fun project (i'm a med student and yes I procrastinate a whole lot to keep me sane :D) I want to create a water injection setup for a dream track car... the 'fun' is in doing a DIY kit that is cheap and effective - I don't particularly care about the car factor I just want something challenging and interesting to do. my dad used to work repairing electronics and currently runs a computer business, guess I get the interest in electronic tinkering from him, I do have an interest in cars (and read this DIY water injection kit thing in an auto mag I'm subscribed too - they said that progressive DIY control could not be done!)

    I've read tonnes of info on it all, and looked at what some of the high end kits offer.

    There are 2 styles of water injection kits that use progressive volume water injection which is far superior to WI that just switches on at a certain point.... it gives progressively more water based on engine demand

    style 1- uses a controller that reads MAP and MAF readings (sine voltages that relate to turbo boost levels and airflow) and subsequently changes the duty cycle of the pump to change the VOLUME of water injected into the engine. the downside of these kits is that in duty cycling the pump the pressure changes and you can get uneven atomisation - probably not that huge a problem. These kits are 400-600 $

    style 2 - uses a controller that is similar to the first style, this controller however progressively on/off switches a fast switching water solenoid while a recirculating style pump maintains a constant pressure. The solenoid switches on more and off less at higher boost whatever to give the engine more water. - this style seems far superior to the first style, not to mention it's about 1000 more haha

    I have read a thread from autospeed.com (water injection part 1) on people very effectively using an expresso vibrating pump (which delivers 200+psi) as the injector pump at $25 bucks its waaay cheaper than a recirculating pump

    the downside is the expresso pump is AC, but the DIY people just use an inverter and hook it all up which is fine - the people however that have done this before just use the system in a way where it just comes on and sprays a constant volume, I want to try to mimic a better kit that progressively sprays more!

    My thoughts
    - I could use the expresso setup with a fast switching solenoid (but use what to switch it on / off progressively more rapidly or leave it on for progressively longer?)
    - I could find a generic recirculating pump and then just duty cycle it with a PWM? This would be what a PWM would be suitable for right?


    Well that's my thoughts for now !
     
  18. Brownout

    Well-Known Member

    Jan 10, 2012
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    Post #5 tells us nothing.

    Thanks for providing the details. I don't know what a fast swtiching soliniod is. Also, I don't know what volume we're talking about. If you know exactly what you need, you might be able to find the correct one by browsning specifications, but I wouldn't have any clue at this point.

    If you found one that could switch fast enough to regulate the volume, then you might be able to use PWM to control it. Keep in mind you'll be dealing with an inductive load, so there will be a built-in delay when you drive it. Also, you'll be dealing with inductive spikes from the soliniod. Have you considered a proportional valve? Something that's opening is proportional to an input, be it a DC level or a PWM signal?
     
    Last edited: Apr 16, 2013
  19. Gibson486

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    Jul 20, 2012
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    PWM into a coil will lead to failures if you do not put the right protection in.....just saying...
     
  20. s900t8v

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    Mar 12, 2011
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