operating electrovalve manually

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dei9
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operating electrovalve manually

Post by dei9 »

hi all,

Just a few questions, so my hydractive ecu is toast... so... while i'm waiting for the my transistors to come, I was wondering if it's possible to operate the solenoid without the waveform? Maybe give it 12v, and step it down to a lower voltage after some time (using a capacitor). I am not sure, what's the general opinion on this?

At what voltage would it give up and switch off, and why is it a bad idea to keep it on at 12v?
(I get that the 1kHz waveform feeds is 12v for quarter of the time thus it thinks it's having 12v all the time, and not having time to switch off.)

Thanks,
D
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Peter.N.
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Re: operating electrovalve manually

Post by Peter.N. »

The reason the supply is pulsed is to reduce the power dissipation in the coil and thus keep the temperature down, if you apply a permanant 12v supply you will probably burn it out. You only need any amount of power to make it switch on but much less to keep it latched. You will need to experiment with a variable voltage supply or a selection of resistors and a meter, reduce the voltage until you hear it drop out, if you don't hear it drop out you can apply the full 12v and you should hear it switch on again. Once you have found the minimum voltage that will hold it in, select a series resistor that will apply that voltage. You can as you mention use a capacitor across the supply so that it charges to 12v to engage the solonoid and the drops to your pre determined voltage when the capacitor discharges, you will probably need a fairly high value, somewhere in the region of 100-1000 uf.

Peter
dei9
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Joined: 17 Dec 2014, 19:47
Location: Liverpool (sometimes Anglesey)
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Re: operating electrovalve manually

Post by dei9 »

Thanks Peter. That's a great answer. I don't have capacitors of that rating lol. So gonna have to shelve this one for now.
Interestingly, it needs 3A to start up, and then only 0.5A to stay latched (if it goes below 0.5A for more than 1.8ms, then it switches off). So it will be resistor free at first, then after 0.5s, the capacitor will introduce a 24ohm resistor thus 0.5A current to keep it running (as per the technical manual).
So my guess is, it can be kept on with a constant voltage of 12v with a 24ohm resistor on it.
I wonder why they didn't design it like this in the first place?
...from Dei

1999 Xantia 2.0 Hdi 110 Exclusive (8396)
2001 Xsara 2.0 Hdi 110 LX Auto
Peter.N.
Moderating Team
Posts: 11563
Joined: 02 Apr 2005, 16:11
Location: Charmouth,Dorset
My Cars: Currently:

C5 X7 VTR + Satnav Hdi estate Silver
C5 X7 VTR + Hdi Estate 2008 Red

In the past: 3, CX td Safaris and about 7, XM td estates. Lovely cars.
x 1199

Re: operating electrovalve manually

Post by Peter.N. »

I would think that if you determine the resistor value first and connect the capacitor across it and switch it to the solenoid, the charge in the capacitor should be enough to engage it then the voltage will decay to the resistance fed value.

You shouldn't have to much difficulty getting large value capacitors, I have drawers full form before I retired from the TV trade, they would be at least 10 years old now but I have used them to repair a couple of sets in the last year or so. Modern sets still use them in the power supply circuits and you can get them for very little money on ebay.

Peter

http://www.ebay.co.uk/itm/1-bag-electro ... 3a9fc9cddb" onclick="window.open(this.href);return false;
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