dump load controller

[methanolcat]

 

   I tried to build this dump load controller designed by CompDoc as it seemed fairly simple and I was able to get all the parts locally.

   http://www.otherpower.com/images/scimages/6828/LoadController_Speedo_Schematic.jpg

   I guess I went about it a little backwards since I spent the time to layout the pcb using "express pcb software", drilled and etched a board, first time for that but it worked out pretty well.  I soldered on all of the components and used an 8 pin socket for the 555 chip to make switching out chips easily done, I did make a mistake in the layout program and thats why the 555 is on the back of the board (all pin's are in the correct position though according to the schematic) didn't catch it until the board was already etched.

   I incorporated the 9v regulator into my layout, and it works, thats the only change I made and I'm not sure that was even necessary since the 555 can handle up to 18 volts.

   All that only to find out it doesn't work, I found out that I had 2 of the pins on  the Tip120 or in my case the NTE261 switched, no big deal, cut traces and reroute them to their right locations. That wasn't my problem though with the pins reversed I had voltage present in "dump" and "charge" mode.

   After all of that and trying to find where I might have made another mistake I couldn't find anything so I bought a proto board as I had hoped to try building it on there and making it work. I put more new components on the proto board double checking every connection as per CompDoc's schematic only to find it doesn't work either.

   Heres what it does do when I connect power, 1 of the 2 led lights will light up, not always the same one, red or green. Changing the position of either one of the variable resistors does nothing as far as the lights go.

   I can however make the opposite led light and it will remain on if I short across C5 or C3. (if red LED or (dump) is lit I can short C3 and the green LED will light and remain lit while red Led goes out, If green LED or (charge) is lit I can short C5 and the red LED will light and remain lit and green LED will go out. All while changing positions of VR1 and VR2 does nothing.

   Also changing the input voltage does nothing other than making the Led's get brighter or dimmer until the voltage is so low that the light just goes out.

   I do get voltage across the output when the red LED is on and not when the green is on as it should be, the circuit just doesn't control this on it's own.

   Not sure this makes a difference since these components should be the same since I cross referenced them to NTE #'s

   Tip120 = NTE261

   2N3904 = NTE123

   7809   = 7805+4v zener or in my case NTE960+4v zener since I couldn't get a 7809

   I've checked and rechecked and the only thing left for me to do is ask for help, it may just be something simple but I'm just not seeing it.

   Any help in getting this to work would be greatly appreciated so thank you in advance.

 methanolcat

  the pin change of the NTE261 can be seen in left side of image near the --

  never used one of these boards before but it sure makes changing things easy





  pcb express software, very easy to use and changes made fairly easy, also a free download





  print out's of your design are easily done as well

[imsmooth]

It is very hard to debug a board over the phone, but I can give you some tips as to what I do when designing or building a circuit.

Using the breadboard is a great start and allows for you to check that the circuit does what it should.  I would build each module in sections.  

First, test with a 9v power supply and take your 9v circuit out of the equation.
Second, assemble the 555 circuit and see if by varying your set point you can get pin 3 to go HIGH and LOW at various SOURCE voltages, where the SOURCE is your charged battery voltage.
Third, I would assemble the dual transistor switch (Q1 and Q2) and see if by raising the voltage going through R10 you can get JP1 and JP2 to short when Q2 conducts.

A simple voltmeter should suffice.

[Boss]

That's an awesome program and a beauty of a DIY PCB

Do you have a link for PCB Express

I know it is frustrating when projects don't work. It seems that after hours of troubleshooting and finding multiple problems it still doen't work.

Many a time I have said, "A Ha!" only to find out I still had more work to do.

I had my own electronics shop for ten years, ten years ago. So I'm seriously rusty.

What tools are you using to trouble shoot with? Scope, I hope?

Is the timer functioning?

On the breadboard, are those new components?

http://en.wikipedia.org/wiki/555_timer_IC

Check Capacitors C1 though C4 to see if triggering is happening

Again a oscilloscope will help a lot.

I hope this helps

[commanda]

I had a look at your pcb layout vs the circuit, and it looks correct. Apart from the fact you forgot to print it mirror reverse. I always put text on the copper side to help avoid that mistake.

First off, remove C1-C4. These are there to deliberately slow the circuit down. Makes debugging difficult. There is a note to that effect on the circuit.

Make sure you're reading those resistor values correctly; those 1% metal films have caught better people than me out before today.

The 555 must run on a stable voltage supply separate from the battery so its internal voltage reference will work as the battery voltage goes up and down. Thats why it needs the 9 volt regulator.

Check with a multimeter that the voltage on the wiper of each pot agrees with an ohms law calculation of the resistive divider for a given battery voltage. If you don't understand this, let me know and I'll do a worked example for you.

Amanda

[Opera House]

Is your 9V really 9v?  You should provide a little extra bias to the zener with a resistor.  Much better would be two resistors and no zener.

If 9V, the trip points will be 3 and 6V if I remember.  Since you already claim to be flyxdexic, you should check the voltages on the pots and components.  You should see the LEDs trip at those points.

[methanolcat]

    Hey Boss heres the link, I have slow dial-up and it took hours for me but it is well worth it, I find it pretty simple to use.

    http://www.expresspcb.com/ExpressPCBHtm/Download.htm

    I don't have a scope (on my want list though), only an assortment of multimeters, digital and analog I mostly use the digital unless I think I may be getting a false reading then I use a meter with the needle and scale just to make sure.

    As far as the timer functioning, I don't know enough about it to tell you but I have several and they all behave the same.

    All of the components are new including the bread board "which I bought after making the circuit board and it didn't work"

  methanolcat

[methanolcat]

    Thanks commanda, and yeah not mirroring the layout was just a newbie mistake on my part, hopefully won't happen again.

    Instead of removing C1-C4 I'm just going to debug at this point on the breadboard since both the assembled board and breadboard function at this point and I didn't use the caps on the breadboard. I did see the note and only added the caps to the assembled board thinking it may behave differently with them but it didn't.

    I rechecked my color codes on the resistors as well as measuring the ones on the breadboard (removed, checked, then put back in place as I know it makes a difference) and other than being off slightly which is typical for 1% metal films, they were all the right values.

    ""The 555 must run on a stable voltage supply separate from the battery so its internal voltage reference will work as the battery voltage goes up and down. Thats why it needs the 9 volt regulator.""

    I did not know this and added it to the breadboard, I did already have it though on the printed board. Does it have to read 9 volts? Mine is reading 7.91 volts across ground and where it should read 9 volts.

    ""Check with a multimeter that the voltage on the wiper of each pot agrees with an ohms law calculation of the resistive divider for a given battery voltage. If you don't understand this, let me know and I'll do a worked example for you.""

    I'm not sure I understand this but I did put my positive meter probe on the wiper terminal and adjusted VR1 my readings ranged from 3.84 volts - 5.6 volts, and for VR2 I got 2.31 volts - 4.76 volts and anything in between depending on the position of the screw for each one. Is this what you meant?, if not I'll need an example.

    I do have some knowledge of the basics, and I am daily searching the internet for as much information as I can grasp and understand. I did take classes in school but that was over 15 years ago I do strive for more electronics knowledge though, it's just going to take some time and plenty of experimenting.

    methanolcat

   

[fallstampa]

seems you are almost there,

 you said,

red led is lit, then you short c3, green then lights.

shorting c3 is pulling pin 2 definitely below its 1/3 threshold since you are taking it to zero.

when you do that,

pin 7 goes high = red off

pin 3 goes high also = green on, = Q2 on = Q1 off,

  releasing the load/disengaging the relay and you are in charging mode.

so one side is working, just not at the correct voltage.

 adjust vr1 for the lowest voltage at the wiper, confirm you have the same voltage at pin2 of 555.

if you do and voltage divider is correct,

r1 in may be to low of a resistance. r1 to low mans the voltage at the wiper will never go below threshold.

hope this helps you, if it does, the other side(vr2) should be easier.

[Boss]

is your username methanolcat because of alcohol racing or maybe biodiesel?

[methanolcat]

Sure is Boss

    methanol (racing alcohol) is what I run in my mud race truck, I'll have to post a couple pic's sometime in a diary just to give you an idea of how crazy it is. From a dead stop my truck as well as many others can make it 200 feet in 4 foot deep mud in 3 seconds or sometimes less, of course it wouldn't matter how deep it was because I'm only skipping across the top of it. We don't start on dry dirt though, we have to pull down into it usually about 16 inches deep on the start line.

   Anyhow we don't call methanol, "alcohol" because too many people confuse it with drinking alcohol.

 methanolcat

[methanolcat]

    I have it working but I had to switch pin 2 and 6, it works as it's supposed to.

 Voltage goes high and dump (red LED) comes on and Q1 conducts.

 Voltage goes low and charge (green LED) comes on and Q1 doesn't conduct.

   I wasn't getting 9 volts out of my regulator I was getting 7.91 volts, I wasn't sure how to correct this with the components I was using so I removed the NTE960 and 4 volt zener and put a LM317T adjustable regulator in it's place so I could dial in exactly 9 volts, anyhow it made no difference in how the circuit reacted at that time, not saying it would have worked as it was but getting exactly 9 volts didn't help my problem.

   Will switching pin 2 and 6 cause any long term problems? if so now that this works how could I make it work as it was? If theres a way to make it work as it was it would save me some headache in trying to switch pins 2 and 6 on my printed circuit board.

  methanolcat

[Boss]

Nr.     Name     Purpose

1.     GND     Ground, low level
   
2.     TR     A short pulse high → low on the trigger starts the timer
   
3.     Q     During a timing interval, the output stays at +VCC
   
4.     R     A timing interval can be interrupted by applying a reset pulse to low (0V)
   
5.     CV     Control voltage allows access to the internal voltage divider (2/3 VCC)
   
6.     THR     The threshold at which the interval ends (it ends if U.thr → 2/3 VCC)
   
7.     DIS     Connected to a capacitor whose discharge time will influence the timing interval
   
8.     V+, VCC     The positive supply voltage which must be between 5 and 15 V, high level
   
   

Strange that switching pins 2 and 6 made it work

[Boss]

Sounds like a killer truck

I'd love to see some pictures

[methanolcat]

   Sorry, one other change, I did add 2 resistors 3.3k each, all inline with R3 (22k) to make the new R3 28.6k because I couldn't get wiper voltage on VR1 up to 6 volts by adjusting it, but I did that before switching pins 2 and 6 and it made no change in operation at that time.

   Do I need to switch 2 and 6 back and change resistor values inline with the pot's to get my 3 and 6 volts opposite of what they are now? Would that make it work?

  At this time I am low (3v) on pin 2 and high (6v) on pin 6.

 methanolcat

[commanda]

Assuming the supply to the 555 is 9 volts.

Pin 2 needs to be less than one third of 9 volts when the battery is 12.1 volts.

So the ends of VR1 should be 2.05 and 4.10 volts.

Pin 2 needs to be greater than two thirds of 9 volts when the battery is 14.5 volts.

So the ends of VR2 should be 4.90 and 7.13 volts.

This can be made to happen by fixing the subtle typo in the circuit, and swapping R3 and R4.

The 555 supply voltage being at 7.91 volts will still allow the 1/3 and 2/3 values to fall within the pot adjustment range.

Amanda

[commanda]

Pin * 6 * needs to be greater than two thirds of 9 volts when the battery is 14.5 volts.

So the ends of VR2 should be 4.90 and 7.13 volts.

See how easy typo's are to make?

Amanda

[methanolcat]

    Thank you commanda, I switched R3 and R4 and removed C1-C4 on the etched board I made and thats all it was, it works just fine now and once adjusted I'll put the caps back in.

    I guess I kinda got there on my own in how I raised the resistance of R3 which allowed me to get the wiper voltage on VR1 up to what I needed, then I switched pin 2 and 6 on the breadboard which put my low voltage side and high voltage side where they needed to be in order for the 555 to work.

    Just that what you found made more since and a lot less changes. Good eye.

   When I started this it looked fairly simple to me up until the point of where it didn't work. The only thing I really knew about the 555 was what was on the back of the package which wasn't much. I looked it up on the internet and found many many things that you can do with it (I now understand the voltage comparator part of it, so thats a start).

   Looking at the circuit I also learned about voltage regulators (including the adjustable regulators) also learned about voltage dividers since there are 2 of them in this circuit and lastly how to use switching transistors although I'm not real sure what the difference is between the 2 I used are other than current carrying capacity (maybe price as well, the cost of the 261 was a bit more).

   Thanks to all who helped with this as I know you spent your time to help me and you could have been doing something more constructive for yourself.  I greatly appreciate it.

  methanolcat

[jeffbirkle]

Nice work. How are things progressing on the circuit?

Sorry but i don't have any info for you now, but i will try to build the same circuit this week and let you know what happens.

I do have some questions for you.

Does anyone have this circuit working?

Could the relays be 40 amp automotive style ( or multiples of ).

How many amps can the circuit handle powering the relays?

If circuit consumption is .025amps plus the relays, and if input from the mill was zero, while in divert mode would the circuit/relays drain the battery bank to the charge setting point then switch the relays off (charge), or would the relays switch off (charge) when the mill drops to zero?

Would it make sense to set the charge setting to 12.8 so battery bank doesn't drain?

Does anyone sell cheap frequency counters?

Jeff

[ghurd]

Jeff,

Not sure why anyone would want to use relays to drive a dump load,

or a relay driver as a dump load controller.

There are a million better ways to do it than how you are thinking.

G-

[methanolcat]

   Jeff, the circuit is finished (debugged) and works great, if you build this all you have to do is switch R3 and R4, I stumbled across one way to fix the problem (not the easiest) about the same time commanda found that R3 and R4 needed switched (easiest and most sensible fix)

   Also I would NOT use any mechanical relays if possible as they are not terribly reliable, a solid state relay would be fine (somewhat expensive), probably the best choice though would be an N-MOSFET in place of Q1 as noted in the original schematic.

[jeffbirkle]

Thanx for the info.

I was looking at n-mosfets, but so far i've only found one that can handle 75 amps.My mill will put out almost 90 amps. I would also like to use this as a diverter not a load ( double throw double pole).

What does the trace c-60 use?

Do you know how many amps the 9v circuit can handle as i may use it to power other circuits?

I have a really nice rpm guage from my auto testing stuff (induction clamp for spark plug wire).Just wondering if it can be converted to use with this rpm circuit?

[ghurd]

Well Done!

I am curious as to why you decided to use that design in particular?

I do not immediately recall anyone having used it successfully.

It does not look very simple to me.

It does not sound simple if the builder can't figure out how it is supposed to, or why it doesn't work.

The locally available parts probably cost more than other options.

The "~30 to 60 second" delay sounds like the extreme opposite of PWM.

Naturally, I am comparing that design to my design.  As shown here,

http://www.fieldlines.com/story/2007/8/24/172521/889

I am not being sarcastic when I say 'Well Done'.  My 1-off devices look like UPS already broke them.

G-

[methanolcat]

 Thanks ghurd

     Originally I was going to build your circuit but some of the parts were not readily available to me (ZM33064, the p-fet's and n-fet's), maybe they were I just wasn't able to cross reference them to something I could buy and not knowing enough about these components I wasn't going to just guess at what might work and later find out it didn't only to be left with a non functional controller.

    I did a search and found some other controllers, checked the store to see if I could get the correct components and it turned out they had what I needed to build this one, so thats why I built it instead of yours.

   I would have rather built yours. Design, assembly, and low part count caught my eye as well as the good comments from other posters who built, bought, and have used yours. It would have been a "WIN WIN" situation if I could have obtained the components as I already know it works.

       ""It does not sound simple if the builder can't figure out how it is supposed to, or why it doesn't work.""

    With a little internet research I was able to figure out how this circuit works and I even figured out how to make it work when it didn't, not as easily as commanda but I figured it out. I guess I wasn't really ready to ask for help when I did as I wanted to figure it out on my own and I wasn't done researching just yet but I wanted to get it working so it could be put to use.

   I'm not very good with electronics yet but I want to learn and thats why I went ahead with the project, learning as I went. I know there are kits out there but I wouldn't have learned anything just by putting one together and using it. I have this strange desire to want to know how the components work and work together so in the future I can design and build my own, for me it's more than just needing a controller.

      ""The "~30 to 60 second" delay sounds like the extreme opposite of PWM.""

   You can use different value caps or even leave them out for rapid switching, the delay on mine is around 3 seconds. I havn't researched much on the PWM at this point.

   Would I want it to switch on and off at a high rate? What would the gain be?

   As far as anyone using it successfully well I guess I can be number 1 on your list, maybe others have built it and couldn't figure out what was wrong with the schematic and how to make it work, but it does work, I'll post completed pic's of the entire setup (controller, battery setup, and inverter) in another post sometime soon as all of this is at my dads house and I don't have any pic's yet.

   Cost was around $30.00 and I have lots of extra resistors, diodes, LED's, etc..... as I bought bulk packs and variety packs, but for my money $30.00 is cheap for what I learned.

   I like that comment about UPS, I better not even go there I know what they can do.   I enjoy your post's keep up the good work.

     methanolcat

   

[jeffbirkle]

Hey Methanolcat.

Are you still using this controller? and is it still working?

I was looking at the original schematic by CompDoc, and i'm not sure if his leads on the LM555 are accurate.

Jeff

 

[jeffbirkle]

Here's a diagram of the LM555.



Jeff

[jeffbirkle]

Oh,I see you've already figured out the LM555.

Disregard that last post as far as LM555.

Jeff