Schematics Variable current 12v 60A to 0A

[ante]

Dazza,

Yes I know the transmitter kind is analogue (0 to X) and the switch is digital (0 or 1). I just thought that in a corrosive environment the digital would have a better chance of surviving thus be more reliable. But this is just me guessing cause I don

[Dazza]

Ante, slew rate control I think is what I'm looking for :), I found one circuit and I'm still searching for more, they seem to be a bit scarce :(. I am not too sure about this one, I'm a little confused on how to put it together. Maybe there is a better circuit to be found. The safety device that I'm leaving to another time, is because the test engine will not be in closed and the risk will be minimal at this stage.

Yes ante, I have no doubt you know what you're talking about, I wanted to be sure I was getting it right that's all ;D, the right name for a particular device.

[Dazza]

Ante, here is the circuit description, I had to zip it because it's a word document.

CIRCUIT_ALLOWS_SLEW_RATE_CONTROL_WITH_INDEPENDENT_RISE_AND_FALL_RATES.zip

[ante]

Dazza,

Is this really what you need? I think it

[Dazza]

Yes ante, this is what I need and I do agree it is complicated :(. As soon as I read the description of this circuit, I realised it worked exactly the way I wanted, controlled the slew rate rise and fall, and then I thought damn it's complicated. You are certainly coming up with some good ways of achieving the effect that I am wanting 8), although I think what you are suggesting will have a stepper affect is this right? If so it will basically create some of the effect that I'm trying to avoid. Adding the ability to control the slew rate rise and fall, will have a positive effect on a lot of the system, one big positive is being able to reduce the amount of hydrogen stored in the hydrogen line, and another is to reduce the effect of horsepower being suddenly drawn from the engine especially if the reactor is demanding higher current, and I am not too sure how the alternator and regulator system, will appreciate being kicked on a fairly regular basis to respond quickly, especially when relying on the idea of using capacitors in the alternator regulators system. I can see that I am likely going to need something to maintain the revs of the engine at idle, if the alternator is drawing too much load from the engine, probably a solenoid but this sort of thing can be sorted out later on down the track. But this slew rate control/dampening effect that I am wanting, will be needed very early in this project. I did find this IC,(DS36C280 Slew Rate Controlled CMOS EIA-RS-485 Transceiver), I am unsure if I can use it, or how to use it.

DS36C280_2.pdf

[ante]

Dazza, No it should not produce a stepper effect, quite the opposite. It should be related to the rpm as well as the throttle position and the output is analogue. The common methods used for maintaining the idle rpm on cars equipped with AC will work even in this application. The DS36C280 isn

[Dazza]

Ante, I think this is brilliant 8), looking at your circuit I can sort of see how it works, and the way you have explained how it should work I can't see any downside. My only problem is that I usually search the Internet for the kind of complete working circuit that I need, and then try to modify it width trial and error to work the way I want. If the components values were chosen near enough for the circuit to work I could take it from their :-\. The amount of time and effort I have put into learning electronics I should know a lot more than I do :(, I probably should take this as a sign to give up. fortunately or maybe I should say unfortunately, I don't give up easily and I have a near endless supply of determination ;D.

I think once I have this circuit on the drawing board ready to put together, I'll have a break from this project for a couple of weeks and comeback with a clear head and a fresh approach. In the meantime I desperately need some basic test equipment especially a MOSFETs tester, which I think a failed MOSFETs is the problem with the PWM that I am using now which has failed. I am thinking of trying to put a transistor tester, Zenner diode tester and a MOSFETs tester, into the one unit :o. I think this could be handy to have three separate pieces of test equipment in the one unit.

Everything has been against me lately ante :(. We've been having frequent storms coming over, usually when I want to use the computer or connect to the net, and the error problems with electronic lad as well as errors with my own computer, is a real pain. The upside is I have had time to do some scavenging, and I have found a lot of handy electronic bits and pieces. I found a heap of old circuit boards I don't know what they're out of, but there is a lot of goodies on them, I've collected 18 12v relays which farnell list as $37 each, and I think there is about 10 24V relays there as well, which aren't the sealed type relay which have some water damage, but still work perfectly, and plenty of IC's and transistors of all sorts. There is also a couple of strange looking components that I have no idea what they are ???.

[ante]

Dazza,

I don

[Dazza]

Yes ante, I will have to put together what I have on the drawing board, and then comeback to this circuit once I have some answers to these unknowns. I am happy that we at least have something to start with :).

In my endeavour to make my own cheap pressure transmitter I have discovered Hall Sensors. And yes here comes the questions ;D. There seems to be a few different types, switch and sensor I am assuming the sensor type will give a varying response influenced by the strength of a magnetic field, I wont have much problem putting together a device that will give a mechanical response to pressure, the problems that I have found is the strength of that response is very poor, not enough to drive any potentiometer or a trimpot that I have found. Have you had any experiences with Hall Sensors, if so can you think of a particular one that could be suitable to try :-\.

ante, if any member of electronic lad, hasn't seen one of Stevens circuit that he has posted, I think they must have their eyes closed ;D ;D. Yes I do want to make as much test equipment as possible myself, much cheaper and I can learn a lot by making it myself 8). Silicon chip magazine gives away a Peak Analyst LCR Meter every month, for the best electronic circuit ideas. I didn't realise just how good that little device was, until I checked out that link you posted :o, I think I will have to add it to my Christmas list.

[ante]

I have tried Alegros 3518 for current measuring just as an experiment not long ago. It

[Dazza]

Yes ante, membrane with a magnet attached to it was the first way I thought of. Then I realised it would be much simpler to attach an electromagnet and sensor, to the moving parts of a regular mechanical pressure gauge. I think an electromagnet would be better for fine tuning and alignment. The Hall sensor that you suggested is not available from Farnell :(. Can you offer me some guidance in choosing an alternative Hall sensor :-\, what characteristics are good and what is not, for this application. Shovelling snow doesn't sound like a good thing to be looking forward to, for the Christmas break >:(, the Aussie Christmas of looking for a shady spot away from the blistering heat in the backyard, to relax with a few cold beers sounds much better 8). Although my partner would disagree, she has always wanted to see a white Christmas. Eventually you wont have to shovel all of that snow out of your driveway, some of it can go into the tank of your car to be melted for fuel ;D.

Well that is another problem that I haven't thought of until now. I have been told about sump heaters? I'm not too sure how they work, I would presume you would have a heating element in your sump, that would be connected to the mains to prevent your engines from freezing. I guess you can add an extra heating element in the reactor, and another in the fuel tank for once the engine is running.

[ante]

Dazza, I am not sure that I know enough to give advice here. This is my first experience with hall sensors that are not supplied to me as a part of a system. I picked this one from one of my suppliers based on small size, 5Volts supply, voltage output and don

[Dazza]

Well I tried this circuit that I posted with a 5V supply, and it worked in a kind of fashion :-\, I'm not to sure where to take it from here. I didn't have the IC specified so I tried a few different ones that I had lain around. With a LM358M I got 2.43V and then the voltage steadily reached 3.72V with the influence of a magnet on the Hall affects sensor. I'm surprised it worked at all ;D.

[ante]

Dazza,

The TL173 will not work properly on 5Volts; you should use 12Volts (10.8

[Dazza]

Sorry ante, I should have mentioned that I was using the (UGN3503U) Hall affect sensor ::). That's why I only supply the circuit with 5V ;D.

[ante]

Dazza,

Ok, then I am very pleased you didn

[Dazza]

Well with some trial and error, actually it was all trial and error ;D, I came up with this circuit. I managed to get an output from 0.56V TO 10V. With the addition of C1, I seem to get a nice smooth rise and fall in voltage. I can't work out how to get rid of the last 0.56V. how are we looking here ante, am I on the right track here 8) ;D.

[ante]

Dazza,

I can see that the non-inverting input is adjustable from 2 to 3 Volts by the setting of R1. The diode D1 lifts U1 from ground by 0.6V and the supply voltage to U1 will be about 4.4Volts (what happened without D1?). The datasheet says minimum 4.5Volts but this might not be a big deal or is it? I don

[Dazza]

Well I wasn't to sure about your suggestion of removing D1, but I tried it anyway ;D. You're answer to(what happened without D1?) Well the Hall sensor didn't like having high voltage shoved up its B_M 12v that is ;D. There is one more Hall sensor left at Dick Smith, I'll have to be extra careful with this one ;). Well I was quite happy with myself, that I managed to get the circuit to work as well as I did, without destroying the Hall sensor. And it took one Swede half a world away to destroy it on me ::). Bad Swede, bad Swede. Just kidding ante ;D ;D ;D ;D, I'll be getting another Hall sensor shortly, and then I'll check and see what the output is from U1 and post the results. Yes the travel in relation to the magnet on the Hall sensor, seems to be pretty good/usable, I am using a fairly large magnet to influence the Hall sensor, so I am not sure how the response will be with a small electromagnet, it should be ok, in regards to the electromagnet, can you offer me any guidance here ante. Basically it's just many turns of wire wrapped around soft iron, I'm just not to sure how I would supply the voltage to it and control it :-\.


I had a look at the website for where you work :D, I can see what you mean when you say, you need a drink on Fridays after work.

Take it easy ante 8).

[ante]

Dazza, I hope your pulling my leg here, cause I can

[Dazza]

yes Ante, something did go wrong it was U2, I replaced it with another and it worked, and I tried removing the diode again and it worked find like you said it would ;D. Removing the diode didn't make any difference, except for having one less component which is good. The output from U1 is 2.43v to 3.62v. I tried using an electromagnet from a relay, and its influence on the Hall affects sensor was a little better than half that of the influence of the magnet. That's not all that good, the electromagnet that I used is about twice the size of what I wanted to use. So I may have to try to use a standard magnet. I wanted to use an electromagnet so I could very it's, strength giving me more opportunity for collaboration :).

ante, just to be sure, yes I was pulling your leg, in regards to it being your fault something went wrong ;D. When you suggested to remove the diode, and I found problems after I done this, I hope you don't think I was pointing the finger at you because something went wrong ???, I would never do that :o, even if you did make a mistake on a suggestion and everything went up in smoke. I was just trying to use some good old Aussie humour, I hope you took it the right way, mate ;D ;D.

[ante]

Dazza,
You have to find a small enough relay to rob the coil from if you really want to have adjustable strength. There are some very small relays out there, the smallest SMD type I don

[Dazza]

Ante, can you give me any suggestions, on how I can reduce the output to 0v, so than the sensor will start responding from 0v to the maximum that I want.

Yes wielding that soldering iron, after a couple of beers probably isn't a good idea ;D.

[ante]

Dazza,

We need to know the output range from the sensor where it is supposed to work (0 to 25psi) or something like that. You have indicated 2.43 to 3.62V, was this the final decision or are there still changes to be done regarding magnets and moving ranges and so on. Until we

[Dazza]

Ante, you mentioned in a previous post, that you didn't know what the output from U1 was, that's what those voltage measurements were from, the Hall sensor. Ok good, we know this circuit will serve its purpose with a little tweaking, once we know how it needs to interact with the other circuits. Thanks ante. Slowly but surely we are moving forward ;).