The overheated regulator and low voltage say to me that there is either a short on the output side (the +5 VDC regulated DC line), or there is an overload on it, or the regulator is wired incorrectly. First re-check the wiring of the regulator, and the part number to make sure it's what you expect it to be.
If that is all okay, next set your voltmeter to semi-permanently connect to any one of the presently too low test points. Then, connection by connection, follow the regulated DC line from the regulator outbound, removing each of the connections to that line individually. At one point the voltage will JUMP back to +5 VDC and that's when you've identified ONE short or overload. Fix that, and if any of the test points STILL reads low, continue on until you've located ALL of the improper connections.
Regards,
Bruce Bates
Bruce-
I just realize that I was using the L78505CV instead of the LM2940-5. I just realize that the L78505CV was outputting 2a instead of 1a like the LM2940-5 and that could of been my problem from the beginning. Could I use the 78L05 with an output of 100ma or do I need to use the LM2940-5? If so then this project is on hold until I order some. Lets just hope I didn't do any real damage, but I most likely did.
The 78L05 should work just fine.· I would suggest that you wire it up and test it out all by itself before connecting anything (anything else) to it.
I guess you're learning something, but probably·not what you'd expected.· I reckon you should take a few steps back, or start over, and go step-by-step.
You may have found your problem, but the ampacity (output amperage) is not the specific problem. The VOLTAGE is what you want to be reviewing. Since you probably have both data sheets handy, and I have neither, please do the following.
Check the general wiring of each, and see if they're basically the same. I suspect they may be, but checking the data sheet is the only way to be sure. Now look in greater details for any REQUIRED capacitors or resistors that the user must supply. Some regulators require them, and others do not. Make sure that the capacitors or resistors which are supposed to be there (if required) are indeed the correct values for the specific regulator you're using.
Once you're sure the wiring is as it should be, disconnect everything from the regulator, and check the regulated output voltage. It should be right on the money. If not, you MUST solve that problem first, before you go any further. Once that looks okay, go back to the steps in my prior message, and remove each load, individually, which is connected to that +5 VDC output line, until you find the culprit.
As far as which regulator to use, you need to take an inventory of the various loads which will be placed on the regulator. Add them all up, and I usually double that amount, just to give myself plenty of "headroom" for possible expansion. Use that total connected load (plus the headroom) to determine which regulator to use, keeping in mind the appropriate voltage as well.
The 78L05 should work just fine.· I would suggest that you wire it up and test it out all by itself before connecting anything (anything else) to it.
I guess you're learning something, but probably·not what you'd expected.· I reckon you should take a few steps back, or start over, and go step-by-step.
PJ Allen-
What I am going to do is start from the beginning and use the 78L05 and each new connection I make I am going to test it with a meter and make sure it stays at +5V and if it drops to low, then I will redo the connection or switch out that componet with a different one.
-Matt
Bruce Bates said...
Matt -
You may have found your problem, but the ampacity (output amperage) is not the specific problem. The VOLTAGE is what you want to be reviewing. Since you probably have both data sheets handy, and I have neither, please do the following.
Check the general wiring of each, and see if they're basically the same. I suspect they may be, but checking the data sheet is the only way to be sure. Now look in greater details for any REQUIRED capacitors or resistors that the user must supply. Some regulators require them, and others do not. Make sure that the capacitors or resistors which are supposed to be there (if required) are indeed the correct values for the specific regulator you're using.
Once you're sure the wiring is as it should be, disconnect everything from the regulator, and check the regulated output voltage. It should be right on the money. If not, you MUST solve that problem first, before you go any further. Once that looks okay, go back to the steps in my prior message, and remove each load, individually, which is connected to that +5 VDC output line, until you find the culprit.
As far as which regulator to use, you need to take an inventory of the various loads which will be placed on the regulator. Add them all up, and I usually double that amount, just to give myself plenty of "headroom" for possible expansion. Use that total connected load (plus the headroom) to determine which regulator to use, keeping in mind the appropriate voltage as well.
Regards,
Bruce Bates
Bruce-
I didn't know it was hot until I was messing around with·a ground wire next to it and I barely touched it and it felt like i got zapped and then when I search around for what caused it I touched the heatsink on the L78505CV and·I was like ouch.· So it might be bad or sorting out.· I am going to look over the datasheets and see if i missed any caps which I think I did.· I will post my findings once I get home, thanks again guys.· Do you think the caps would keep it from getting hot or do you think thats an internal problem of the regulator?
The capacitors would make it run hot if they were placed in circuit backward (i.e. their polarity was not observed) and given enough reverse voltage they might even go bang!
Well, I used a couple of different caps on this schematic which are all NP. I don't know if that also can be part of the problem. So what I am going to do is make sure I have all the right components needed down to the polarization and test to make sure that they all are working the way they should before I put this circuit together and that might help with the problem.
Unfortunately, I do not have the .33 uf or the 0.01 uf on hand. What do you guys recommend as the best substitute for them for this circuit? Also who recommends using the MAX232 over the resistor - transistor setup they have between the DB9 and the BASIC 2 Stamp?
· What do you have on hand?· I figure anything up to 4.7uF would be OK.· Put the parts in, turn it on, measure your input and your output.· Turn it off.· Place a 1K resistor across the output (output to ground), turn it back on and measure it again.
· When you·place your PIC, connect all the GNDs first.· Step by step by step.
The 1uF should be OK.· Place them, check it; then place the load resistor on the output and check it again.· Give it a whirl.
I was think the PIC had more than one Ground/Vss PIN, but it doesn't, from looking at that schematic on Page 1·(when components/ICs have more than one Ground pin, and it's not unusual, it's important that they all get there.)
Okay, here are the steps I am going to take:
a) Connect the 78L05 to a wall adapter and test its output.
b) Connect (i guess 2) 1uf CAPS and test the output.
c) Connect a load resistor from the output to the ground and test the output (I don't know what this does).
d) Connect the 78L05 to the PIC and connect the gnd terminal and test the output.
Then I will post the results here in 10 mins or so.
No, man -- it has to have the CAPs to work, so place them first/beforehand., combine your "a" & "b" steps.· Placing the load resistor proves that you can pull some current (with 1K, it's 5mA.)· This is more fun than a barrel full of people.
LOL thanks PJ for the schematic but I figure out where the 1k should go using common sense(Need to use more of that haha).
Here are the results:
The LM78L05 with the 2 1uf Caps show an output between 5.06 and 5.07.
The LM78L05 with the 2 1uf Caps +1k load resistor shows an output of the same thing
Connecting the LM78L05 with 2 1uf Caps +1k load resistor to the PIC, the PIC is showing an output of the same thing. I don't know if this is correct or if I am testing it correctly.
It sounds to me that you have a good start, now, Matt.· Just keep going, you have abaseline to procede from.· Turn it off, place a component, and see if it goes bad.· If you have an LED, place it in series with that resistor, and if you do something that's not right, you'll know because the little red light won't be on.
Thanks for your help so far. One more thing and that is the MAX232. I think that would be easier to setup, its just needs the right CAPS right? I am going to have to take a look at its data sheet and see which ones it needs. I will post an update in a hour or so.
Most MAX232s use 1uF Caps, too.· The ST232 uses 0.1uF (kinda cool, it.)· Just play it step by step, build up your confidence.· I'm going to be snoozing here shortly, so I'll get back to you tomorrow.· The MAX232 will result, if successful, in having two more voltages to measure -- +10V (Pin 2) and -10V (Pin 6).
PJ Allen said...
Most MAX232s use 1uF Caps, too. The ST232 uses 0.1uF (kinda cool, it.) Just play it step by step, build up your confidence. I'm going to be snoozing here shortly, so I'll get back to you tomorrow. The MAX232 will result, if successful, in having two more voltages to measure -- +10V (Pin 2) and -10V (Pin 6).
Nevermind using the MAX232 becuase I can't get a clean 10v source, I am working with a 9v adapter. I guess I will be using resistors and transistors for this.
I'm working with the MAX232 as well... I have the same poblem (no 1 uF polarized electrolytics on hand). In my post, I got back a response from PJ ALLEN saying that you can substitute 1uF non-polarized Tantalum capacitors... do you have any of those? FYI... here is the thread.... http://forums.parallax.com/forums/default.aspx?f=5&m=104911
Matt -- Go ahead, use the 1uF caps, they're fine.· It just needs the capacitance, the type isn't such a big deal here.
Only thing is, don't connect it to the PIC till it's fully ready, connecting it to the PIC should be the last thing to do in this project.· Like Forrest wrote, it generates, if you will, the +10V and -10V that I mentioned.
Steve Joblin -- Did you make that circuit up yet or what?· It just needs the capacitance, the type isn't such a big deal here.
Two guys, Matt and Steve,·with nothing but 1uF Caps, and non-polarized.· They must be big.· Are they on sale some place?
Matt -- Go ahead, use the 1uF caps, they're fine. It just needs the capacitance, the type isn't such a big deal here.
Only thing is, don't connect it to the PIC till it's fully ready, connecting it to the PIC should be the last thing to do in this project. Like Forrest wrote, it generates, if you will, the +10V and -10V that I mentioned.
Steve Joblin -- Did you make that circuit up yet or what? It just needs the capacitance, the type isn't such a big deal here.
Two guys, Matt and Steve, with nothing but 1uF Caps, and non-polarized. They must be big. Are they on sale some place?
PJ Allen-
Okay, thanks for the warning. In about 10 mins I am going to work on this circuit for a bit. I wanted it to be done last night but I had the question about the NP and Polar Caps. Hopefully I can see where I went wrong and get this thing working today.
11:35am
I connect the MAX232 to the LM78L05 and pin 6 is showing an output of -8.81V and pin 2 is showing an output of 9.25V.
Steve- Your 1st image is a great help but your second image is a little confusing. Thanks though.
12:41pm
I have everything connect and doubled check to make sure every connection is correct and I plug it in and ran the basic stamp editor and its still a no go. I am going to change how I have pin 28 on the BS2 connected and try it again later.
Post Edited (Matt Battle) : 1/15/2006 5:44:13 PM GMT
Comments
Bruce-
I just realize that I was using the L78505CV instead of the LM2940-5. I just realize that the L78505CV was outputting 2a instead of 1a like the LM2940-5 and that could of been my problem from the beginning. Could I use the 78L05 with an output of 100ma or do I need to use the LM2940-5? If so then this project is on hold until I order some. Lets just hope I didn't do any real damage, but I most likely did.
-Matt
The 78L05 should work just fine.· I would suggest that you wire it up and test it out all by itself before connecting anything (anything else) to it.
I guess you're learning something, but probably·not what you'd expected.· I reckon you should take a few steps back, or start over, and go step-by-step.
You may have found your problem, but the ampacity (output amperage) is not the specific problem. The VOLTAGE is what you want to be reviewing. Since you probably have both data sheets handy, and I have neither, please do the following.
Check the general wiring of each, and see if they're basically the same. I suspect they may be, but checking the data sheet is the only way to be sure. Now look in greater details for any REQUIRED capacitors or resistors that the user must supply. Some regulators require them, and others do not. Make sure that the capacitors or resistors which are supposed to be there (if required) are indeed the correct values for the specific regulator you're using.
Once you're sure the wiring is as it should be, disconnect everything from the regulator, and check the regulated output voltage. It should be right on the money. If not, you MUST solve that problem first, before you go any further. Once that looks okay, go back to the steps in my prior message, and remove each load, individually, which is connected to that +5 VDC output line, until you find the culprit.
As far as which regulator to use, you need to take an inventory of the various loads which will be placed on the regulator. Add them all up, and I usually double that amount, just to give myself plenty of "headroom" for possible expansion. Use that total connected load (plus the headroom) to determine which regulator to use, keeping in mind the appropriate voltage as well.
Regards,
Bruce Bates
What I am going to do is start from the beginning and use the 78L05 and each new connection I make I am going to test it with a meter and make sure it stays at +5V and if it drops to low, then I will redo the connection or switch out that componet with a different one.
-Matt Bruce-
I didn't know it was hot until I was messing around with·a ground wire next to it and I barely touched it and it felt like i got zapped and then when I search around for what caused it I touched the heatsink on the L78505CV and·I was like ouch.· So it might be bad or sorting out.· I am going to look over the datasheets and see if i missed any caps which I think I did.· I will post my findings once I get home, thanks again guys.· Do you think the caps would keep it from getting hot or do you think thats an internal problem of the regulator?
Well, I used a couple of different caps on this schematic which are all NP. I don't know if that also can be part of the problem. So what I am going to do is make sure I have all the right components needed down to the polarization and test to make sure that they all are working the way they should before I put this circuit together and that might help with the problem.
-Matt
Unfortunately, I do not have the .33 uf or the 0.01 uf on hand. What do you guys recommend as the best substitute for them for this circuit? Also who recommends using the MAX232 over the resistor - transistor setup they have between the DB9 and the BASIC 2 Stamp?
Thanks guys and have a good day.
-Matt
· What do you have on hand?· I figure anything up to 4.7uF would be OK.· Put the parts in, turn it on, measure your input and your output.· Turn it off.· Place a 1K resistor across the output (output to ground), turn it back on and measure it again.
· When you·place your PIC, connect all the GNDs first.· Step by step by step.
The smallest I have are some 1uf NP and some 10uf NP.
When you said "When you place your PIC, connect all the GNDs first. Step by step by step." Do you mean test the volt output on each ground terminal?
-Matt
I was think the PIC had more than one Ground/Vss PIN, but it doesn't, from looking at that schematic on Page 1·(when components/ICs have more than one Ground pin, and it's not unusual, it's important that they all get there.)
a) Connect the 78L05 to a wall adapter and test its output.
b) Connect (i guess 2) 1uf CAPS and test the output.
c) Connect a load resistor from the output to the ground and test the output (I don't know what this does).
d) Connect the 78L05 to the PIC and connect the gnd terminal and test the output.
Then I will post the results here in 10 mins or so.
Post Edited (PJ Allen) : 1/15/2006 3:47:08 AM GMT
Here are the results:
The LM78L05 with the 2 1uf Caps show an output between 5.06 and 5.07.
The LM78L05 with the 2 1uf Caps +1k load resistor shows an output of the same thing
Connecting the LM78L05 with 2 1uf Caps +1k load resistor to the PIC, the PIC is showing an output of the same thing. I don't know if this is correct or if I am testing it correctly.
-Matt
It sounds to me that you have a good start, now, Matt.· Just keep going, you have abaseline to procede from.· Turn it off, place a component, and see if it goes bad.· If you have an LED, place it in series with that resistor, and if you do something that's not right, you'll know because the little red light won't be on.
Thanks for your help so far. One more thing and that is the MAX232. I think that would be easier to setup, its just needs the right CAPS right? I am going to have to take a look at its data sheet and see which ones it needs. I will post an update in a hour or so.
-Matt
Nevermind using the MAX232 becuase I can't get a clean 10v source, I am working with a 9v adapter. I guess I will be using resistors and transistors for this.
-Matt
-Matt
Matt -- Go ahead, use the 1uF caps, they're fine.· It just needs the capacitance, the type isn't such a big deal here.
Only thing is, don't connect it to the PIC till it's fully ready, connecting it to the PIC should be the last thing to do in this project.· Like Forrest wrote, it generates, if you will, the +10V and -10V that I mentioned.
Steve Joblin -- Did you make that circuit up yet or what?· It just needs the capacitance, the type isn't such a big deal here.
Two guys, Matt and Steve,·with nothing but 1uF Caps, and non-polarized.· They must be big.· Are they on sale some place?
PJ Allen-
Okay, thanks for the warning. In about 10 mins I am going to work on this circuit for a bit. I wanted it to be done last night but I had the question about the NP and Polar Caps. Hopefully I can see where I went wrong and get this thing working today.
-Matt
Post Edited (Steve Joblin) : 1/15/2006 4:11:14 PM GMT
11:35am
I connect the MAX232 to the LM78L05 and pin 6 is showing an output of -8.81V and pin 2 is showing an output of 9.25V.
Steve- Your 1st image is a great help but your second image is a little confusing. Thanks though.
12:41pm
I have everything connect and doubled check to make sure every connection is correct and I plug it in and ran the basic stamp editor and its still a no go. I am going to change how I have pin 28 on the BS2 connected and try it again later.
Post Edited (Matt Battle) : 1/15/2006 5:44:13 PM GMT
·· What was the problem with your BOE Full Kit?· I looked back through the thread and you never mentioned anything about it that I can find.
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