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Topic: 3 wire solenoid (Read 8582 times) previous topic - next topic

dc42

Either can be made to work, but the lower diagram is conventional and is more efficient.
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srusha

I connected it that way (the lower one)..

so why doesnt it work that way?

btw. the pulses are pretty quick.. about 100ms (maybe I'll try less, 50 or 10 ms).
does the power loss really matter when its so quick?

dc42


I connected it that way (the lower one)..

so why doesnt it work that way?

btw. the pulses are pretty quick.. about 100ms (maybe I'll try less, 50 or 10 ms).
does the power loss really matter when its so quick?


What value resistors are you using, and what is the resistance of L1?
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srusha

I tried using values that range from 200~ohm to 10k ohm,  I will check the solenoid resistance soon.

thanks.

srusha

ok, it works, thanks guys,

A small note;
a DC solenoid might require 2 9v batteries, in paralleled connection. (I guess it is obvious but I lost alot of hours on that)

Grumpy_Mike

Quote
a DC solenoid might require 2 9v batteries, in paralleled connection. (

Never, never connect batteries in parallel, they cross charge.

Never use 9V square batteries in motor or solenoid circuits, they have very little current capacity and will very quickly drain.

srusha

What? why not?

I just connect the positives together and the negetives together, whats the problem? and how do I attach them like that (maybe a diode attached?)

I have a DC irrigation valve that uses 2 9v square batteries, in order to latch the solenoids they have to be paralleled, the solenoid is latch so the drain should be negligible...




dc42

If you must use a 9v battery for that application, I suggest you use a lithium one. They are good for higher currents than the alkaline sort, see http://data.energizer.com/PDFs/la522.pdf. It sounds to me that you are only providing a short pulse to the solenoid, in which case a large capacitor (several thousand uF) in parallel with the battery will help too.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

srusha

Actually that sounds like a great idea!

I will try that tomorrow.

but still, I dont see why using 2 batteries in parallel (with diodes) could do any damage..

dc42

2 batteries + diodes, connected in parallel, is OK. 2 unused batteries out of the same pack of 2 (or more), connected in parallel without diodes, will generally be OK because the batteries should be well-matched; but there is a small risk that if one of the batteries develops a fault, then a lot of heat could be generated. One fresh battery in parallel with one used battery, or a lithium in parallel with an alkaine, is asking for trouble unless each battery has a series diode.
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Grumpy_Mike

Quote
What? why not?

I told you. They will cross charge.
That means that the battery with the higher voltage will try and charge the battery with the lower one. This is not good for the cells and will cause them to become damaged. Using diodes from each batter will stop this from happening.

srusha

Yeah, I already have done that, thanks for the heads up.

Docedison

There is a little "Trick" that worked well for me and about 1500 radio operated solenoid controllers I built in the 90's... Use a 100 to 470 ohm resistor between the batteries and a 4700uF cap... Keep your pulse width at 100 mS (that was I found almost the perfect time because it provides damping for the solenoid as well). The israeli's make a half dozen different solenoid controllers for and frequently including the solenoid and a valve as well for lawn irrigation control for homes AND Guess what...., They ALL use those 9V transistor batteries. If you take 10 minuted to charge the capacitor it is a small drain on the batteries... But the cap is charged up more than enough to operate the solenoid, Every Time. The rest of the clock (controller) is a Very low power micro controller and most will last for 6 months before the battery needs to be changed.

Doc
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srusha

the biggest capacitor I have is only 100u, do you think thats enough?

majenko


the biggest capacitor I have is only 100u, do you think thats enough?


No, but 47 of them in parallel will give you around 4700µF...

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