Not impressed so far

sjp

New Member
so I tried my first circuit.

placed a picaxe 5v reg, decoupled it (100n) added 4.7uF to its input.. Added a 12V rail and interactive switch. Added a 5V relay.

turn interactive switch on... Relay ON,

Turn interactive swicth off ......... relay wouldnt turn off. Investigated properties of relay and found its drop out voltage to be 1V.

Added probe to regulator O/P .... probe shows when switch off, output is 1.93V

Pulled the output down viz 10k....... No luck... Then tried 100Ohm ... Still 1.93V.

So whats going on?

Anyone know?
 
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sjp

New Member
Thanks BeanieBots,,, I cant do much right now as I am in the office.. But if it helps, I did do some more "playing around" last evening.

The aim is to find a solution to the wretched TB6560 "power up" "power down" sequence.... In fact I dont know why I am bothering to simulate it, because I already have the answer in my head.. Simply apply 5v to the logic 1st and simultaneosly to a 5V relay. The relay then switches 24v through to the motor drive pins.. I also intend to hold up the logic with 20uF or something... Maybe some low impedance across the 24V to make sure that the Elctrolytics upstream discharge quickly in the case of sudden mains failure.

Anyhow, way off topic. So having had VSM for all of 15mins, yet familiar with Lspice and ISIS, I added a 5v regulator to a blank canvas.. ( it didnt seem to mind which reg was used).. I then added a 5V relay. Finally an interactive switch.

Ground and 12V terminal.

When I first saw the problem, (relay didnt turn off) I added a probe to the 5V output.. I noticed that the 5V went down to 1.93V after the switch (input side of regulator) was forced "off" ... Then I researched the relay and see that it has a min drop out voltage of 1V.
So that explained why the relay wasnt turning off.

Then I thought well maybe I havent met the real life conditions expected around a regulator and that VSM behaved the same way.

So I started adding decoupling caps 100n and also 10uF, just as it you had a real life scenario, still the same.. So I added a low impedance load (100 ohm) across the output of the reg.. Still no luck.

At which point I gave up.

However, if the DVM is left in place across the output of the regulator and the circuit iis "run" with just the "pl;ay" and "stop" buttons..... then the cct behaves as expected.. The DVM drops back to 0V.

When the interactive switch is inserted between 12V terminal and Reg input, the cct is made to "run" and just the momentary switch is used to switch power through to the reg or not... then I see the problem, the ouput of the reg never falls back to zero..

So I guess the cct with all of 4 components is wired correctly since it simulates ok with RUN/STOP, but then I suppose the DVM will display sero, since in the stop mode it is no longer simulating.

When I get home I will post the cct.

Thanks
 
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Technical

Technical Support
Staff member
There are many example circuits, both PICAXE and general electronics, so we suggest you work through these so you can see how circuits simulate.
 

sjp

New Member
beanibots here is circuit

Technical.. Not impressed by reply, its like telling someone to RTFM. A little more guidance would have been nice.

Thanks for help Beaniebots, here is circuit.. Read the chapter on "configure power rails" couldnt see anything obvious.. Checked netlist and all seems clear

There are many example circuits, both PICAXE and general electronics, so we suggest you work through these so you can see how circuits simulate.
 

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techElder

Well-known member
Is this a real circuit or a simulated circuit? You've drawn a basic regulator circuit, but you've mentioned a relay which isn't in your circuit schematic.

Your additional comments ("... Not impressed by ...") don't add much to the solution and won't entice many to join in. Perhaps a language translation problem?
 

BeanieBots

Moderator
Unfortunately I no longer have a working installation of VSM so I cannot replicate your circuit.
Looking at it, I cannot see anything obvious but as technical have said, there are ways/rules about power rails and I've fallen into such traps myself.
That said, I would expect the meter in your layout to read zero.
Hopefully somebody who knows the product better than I do can offer an explanation.
 

sjp

New Member
ok thanks beaniebots, I am glad that its not just me.. I have looked and looked and cant see anything either (as the net list suggests)

Oh and to Texasclodhopper, I paid £60 odd quid for it, I'll say what I want.

The relay was taken out, since I did not want to confuse anyone. In fact you can take out all the passive components supporting the Regulator, it makes no difference..
In fact if you remove the regulator and just link the input to the output, the simulation is good.. Zero volts read on the DVM when the switch is open.. Only when you insert the regulator do you discover you have 1.93v when the switch is off. ( not much good if the first project is to design a power supply)

And yes I feel as though I have a beef with Technical, I paid £60, and I am still waiting for the courtesy of a reply to my email on their email support route.

I have used Ltspice, I currently use Altium ( at work), I have used Proteus, its not like I am new to the subject, I don't expect to be told to refer to example circuits to see how they simulate. Clicking on a power terminal in an example circuit is not going to tell me much, there is far more information in the paragraphs surrounding the "power rail" subject, (All of which I have already done, prior to entering the forum.).....so his suggestion was not helpful at all. If that is typical of the assistance offered then I don't want to bother with VSM, I'll stick to Ltspice and save my money.

PS.. The simulation is identical even if the source is a battery ( 1.93 volts when the switch is up)
 

Technical

Technical Support
Staff member
and I am still waiting for the courtesy of a reply to my email on their email support route.
We aim to respond within 1 working day. We also do not generally duplicate the same replies on both the forum and email at the same time.
We have requested your .dsn file by email so that we can test it and make sure the rails are configured correctly. We have built similar circuits here with a 7805 and they seem to give a clean 5V/0V as expected, so something appears to be incorrectly configured in your file.

Also what value resistance is the 'off' property of your switch set to (right click, edit properties)?
 
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Technical

Technical Support
Staff member
Labcenter have confirmed there is a minor fault in the 78xx regulator models which they will fix.
The simple way to workaround the issue is to not cut off power to the 5V regulator, when it is on it simulates fine.
Alternately a diode between the switch and the regulator input also seems to fix the issue.
 

sjp

New Member
Thankyou for your swift action.



Labcenter have confirmed there is a minor fault in the 78xx regulator models which they will fix.
The simple way to workaround the issue is to not cut off power to the 5V regulator, when it is on it simulates fine.
Alternately a diode between the switch and the regulator input also seems to fix the issue.
 
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