Hi Guys (Posted this on alt.electronics but it seems like only spam lives out there)
I need to use 70V to power a solenoid for about 1sec at a time. I would like to controll it with a PIC microcontroller.
What would be the best to get the 5V of the pic to activate the 70V circuit of the solenoid? Is there any super transistor or is the only way to do it by using a relay? Can somebody give me some google keywords to find the right component to use and the applicable attributes that I need to look out for?
In addition to that, I don't know how to get 70V from anywhere. Preferrably, I want to get it from the wall socket. The transformers I can find is only betwen 3V and 24V. I'm in Europe. Where can I buy something that I plug into the wall and get 70V out. Again a few google keywords will be helpful.
Safety: The 24V doesn't seem to shock me at all. Will 70V give you a shock?
Thanks!
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M
mc
Given that it's a solenoid, and the effects of getting 70 V into your PIC circuit would be diastrous, I would recommend a relay. There are transistors you can use -- the IRL series of MOSFETS from International Rectifier Corporation. But a relay isn't going to slow down the solenoid, and it's simpler and safer.
70 V at how many amps?
You're probably going to have to design and build your own power supply. Even then, finding a suitable power transformer may not be especially easy.
Where did you get the solenoid? What kind of power supply would it be using if you weren't involved?
Will the solenoid run on AC? Maybe 120 V through a resistance?
Yes!!!! And 24 V will too, if conditions aren't just right.
70 V is most definitely high voltage, not appreciably different from the
120-volt line.
C
Chris
So John Fields' responses were spam? Smells kind of turkey-ish to me.
C
coetzee.evert
quoted text -
No not at all. I posted the spam comment before JF started assisting. This forum looks more active so I though i'll try here as well.
C
coetzee.evert
Hi MC
I'm using a 24V wallwart PSU which works perfectly. So in a perfect world I'll just buy a similar (but halfprice of course ;-) ) 72V version and everything works. Calculations by JF shown that it will be about 3.4A that will be drawn.
J
John Fields
quoted text -
Crosspost. :-)
C
coetzee.evert
Hide quoted text -
What does that mean? You're withdrawing the only support I got with this? PLEASE dont!
J
John Fields
Hide quoted text -
LOL, I haven\'t withdrawn support at all. :-)
All \'crosspost\' means is not to make the same post first to one
group and then to another, but instead to include the names of both
newsgroups in the "Newsgroups:" line. (The line which determines
where your post is going, whatever it may be called)
That way whoever answers your post (whichever newsgroup they may be
in) will send copies to all the other newsgroups listed and won\'t
have to go to each individual group to post.
Posting to each group separately is called multi-posting, while
posting to them all at once is called crossposting, which is
generally preferred in most related groups.
I\'ve crossposted this post to alt.electronics,
sci.electronics.basics, sci.electronics.design, and
sci.electronics.misc, so if anybody\'s interested they might also
join in.
D
default
If the solenoid is working on 70 VDC an open collector NPN switching transistor driven from the PIC would be all you need assuming the ground of the pic and ground of the solenoid don't require isolation.
Optical coupler switching an isolated transistor is another good way and keeps the hash and high voltage at arms length from the pic. No chance inductance causing the pic to reset or other ground loop problems.
70 volts AC - use a solid state relay operating directly from the pic
- common activation on the "coil" side is 3-32 VDC at 10 milliamps, and AC side 24VAC to 240 VAC (but check specs). Optical isolation is normal for SSRs.
70 volts? That might be doable with lots less. Solenoids are usually specified with a "must pull in" voltage and a "hold" voltage (much less) and a "must release" voltage. A tiny free running inverter could create the voltage from whatever you have to work with. Depends on how much power you need.
If it is 70 V AC solenoid it will pull in on lots less with DC. 24 volt transformer rectified and filtered will give you ~36 DC and may be enough for an AC rated solenoid.
For audio amps running from mains supplies 50-100 volts is a common requirement so there aught to be some transformers.
Unless the solenoid needs a high current, a voltage doubler or tripler (search the web to see how with diodes and caps) to boost the voltage. Then you still may get it working with a lower current supply by using the doubler to charge a cap, dumping the energy in the cap to pull in the solenoid then keeping it in with the sagging voltage when the cap is discharged.
70 volts will shock. 12 volts will shock with an open cut and salt water on one's hands. But a 70V shock isn't nearly as bad as 220. I used to play with B batteries from tube radios when I was a kid. The
54 volt batteries would tingle, 90 volt battery might get your attention, and 22 volt batteries wouldn't even be felt with dry skin.
70 volts is reasonably safe in my opinion. A lot depends on how exposed and what's at stake. Unlikely you'd kill yourself the first time you got across it. A sudden muscle contraction on DC might do more damage than the electricity.
To kill requires something like 100 milliamperes of current through a vital organ - or so I was taught - I doubt they tested that empirically and all people are different . . . Skin resistance can be below 700 ohms.
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