Voltage regulator problem

[CDRIVE]

I only need a constant 9 volts out to get it where I need it but cant find a DC source that works. I can touch the heat sink about 3 seconds before I have to let go

A few things to mention.. First off the 9V battery is the weakling of the carbon battery family. Never rely on them for anything that needs juice. Secondly, A DC input should work on this regulator but the DC voltage should be 24 x 1.413. This is because the 24VAC spec on that page is an RMS value. It translates to 33.91V Peak. It's the peak value that you would need if the input is DC. So the DC input should be 33.9VDC.

Now comes the worse news. Since you only want 9VDC out this reg is a bad choice unless we can modify it. This is because you really only need a 12V overhead to feed a 9V regulator. Any more than that will waste power in heat dissipated by the regulator.

Now here comes a really dumb question. If you only needed 9VDC then why feed 2 series 9V batteries into a regulator? Though the 9V bat is a weakling it would have performed better connected directly to your load. In fact two fresh 9V batteries in parallel would have been preferable than two in series powering the regulator.

Chris

 

[bdg]

Thanks very much! That helps a lot. I figured there was something about 9V batteries. I put 2-9volts together to boost the voltage. Since I was not getting enough out of the 8AAs I thought I would try the 9s. The reason I did not connect the 9 directly into the load is that I need to be able to regulate the heat. Sometimes it needs to back off a little. By the way, I see you are in South Florida. How far South? I am in Miami

Brian

 

[CDRIVE]

Hi Brian, I'm about 50 miles north of you in south PBC.

If you're going to run this off batteries you'll need to change course a bit. You haven't told us what your load current is but it would seem you need more current capabilities than small carbon batteries will deliver. Have you considered a 12V Nicad or Lipo pack? A series stack of D cells can deliver juice but will take up considerable real estate.

The 12VDC input voltage presupposes that we can modify your regulator or design a new one for ya.
Questions: Are you desirous of keeping the kapton thermofoil heater temp constant automatically? Are you in school or do you work in Bio-Med Electronics, other?

Chris

 

[bdg]

Hi Chris,
I am sorry for not answering the load question but I don't know the answer to that. I may have thought that needing 9 out was the answer but now I am sure that is wrong. The kapton would need to be adjustable because it heats up a clay based material that a patient may find is too hot against the skin. I will look into the 12V NiCad and Lipo pack. I am a business owner not related to the industry but my wife is a neuro scientist that works with eye related issues and that is where I got my idea. Do you ever take on projects or do consulting work outside of the forum?

 

[CDRIVE]

Hi Chris, I am a business owner not related to the industry but my wife is a neuro scientist that works with eye related issues and that is where I got my idea. Do you ever take on projects or do consulting work outside of the forum?

I'll have to ponder that. I was a bio-med consultant/contractor prior to retirement. My liability insurance was obscene! Not anxious to go there again. What I do here is strictly magnanimous. If we go where you're suggesting it's strictly obscene profits on my end.

Chris

 

[bdg]

I'll have to ponder that. I was a bio-med consultant/contractor prior to retirement. My liability insurance was obscene! Not anxious to go there again. What I do here is strictly magnanimous. If we go where you're suggesting it's strictly obscene profits on my end.

Chris

Ok, give it some thought. I could be chasing my tail forever so depending on just how obscene It would most likely be worth it for me in time savings (and getting it done right), and I may learn something in the process instead of throwing things at a wall until something sticks

 

[CDRIVE]

Brian, You'll be amazed at what we'll do for you absolutely free! We have great minds here. Don't be in a rush to spend your money. Do you have soldering experience? Can you read a schematic? If you can do both we can instruct you in building a prototype.

Chris

 

[bdg]

Brian, You'll be amazed at what we'll do for you absolutely free! We have great minds here. Don't be in a rush to spend your money. Do you have soldering experience? Can you read a schematic? If you can do both we can instruct you in building a prototype.

Chris

Hi Chris,
I have bought most of what I need. Solder, bread board, resistors, capacitors etc. I don't know how to read a schematic but will work until I do. I did a lot of research and watched plenty of youtube videos on how to create this circuit. I did not think it would be easy but it was frustrating and I was not able to get it to work and that is why I bought one. Even simple circuits were hard to translate from a breadboard to a circuit board. What is the best way to get started? I wound up crossing over responses, answering different questions and not responding to others on the blog and I want to keep that in check so I don't irritate people trying to help. I studied videos like this one a lot but just could not get it to work. I used the exact resistors, capacitors and the LM317. The only thing I was able to accomplish was to burn out the pot.

not being able to get it to work was very frustrating because I know this is simple for people who know what they are doing.

 

[CDRIVE]

Well, if everyone knew everything Electronics Point would be ... uh... pointless!

Damn, that's a good pun! I'll just have to remember not to use it again.

Moving a circuit from a Protoboard to a PC board is most easily accomplished by using Stripboard that can be purchased at Radio Shack. You're in Miami so you should have plenty of suppliers down there.

I'll be posting something for you but first I need you to post the link to the device you're powering. We need to know its current draw..

Chris

 

[(*steve*)]

Moving a circuit from a Protoboard to a PC board is most easily accomplished by using Stripboard

I think that it is worthwhile pointing out that this is not a trivial step and the fact that you're having trouble with it (especially if just conceptually) is an indication that you are developing an understanding.

 

[bdg]

Well, if everyone knew everything Electronics Point would be ... uh... pointless!

Damn, that's a good pun! I'll just have to remember not to use it again.

Moving a circuit from a Protoboard to a PC board is most easily accomplished by using Stripboard that can be purchased at Radio Shack. You're in Miami so you should have plenty of suppliers down there.

I'll be posting something for you but first I need you to post the link to the device you're powering. We need to know its current draw..

Chris

Hi Chris,
here is a link to the heater I purchased let me know if you need additional info and I will get it for you http://www.ebay.com/itm/MINCO-KAPTO...HEATER-MINCO-HEATER-HK5561R37-4-/370880973198

 

[bdg]

Thanks Steve, I am getting a very base level of understanding. At least when I go into Radio Shack I can say with confidence. "I need a LM317 with a heat sink" and everyone around will think I know what I am talking about, and hopefully not ask me any questions.

 

[(*steve*)]

I'm not sure you should jump too far ahead until we know the rated current of that heater...

OK, 37 ohms, that will give you about 250mA at 9V.

I think you need to tell us why you want to regulate the voltage to this. Do you want to vary the voltage to change the temperature? There are better and more efficient ways.

 

[bdg]

I'm not sure you should jump too far ahead until we know the rated current of that heater...

OK, 37 ohms, that will give you about 250mA at 9V.

I think you need to tell us why you want to regulate the voltage to this. Do you want to vary the voltage to change the temperature? There are better and more efficient ways.

I do need to be able to regulate the temperature between 110 and 130 degrees The size of these heaters work well and that is why I chose them. If there are alternatives with more or less the same dimensions I am certainly open to it

 

[CDRIVE]

Thanks Steve, I am getting a very base level of understanding. At least when I go into Radio Shack I can say with confidence. "I need a LM317 with a heat sink" and everyone around will think I know what I am talking about, and hopefully not ask me any questions.

Actually no. The odds are and if you're alone in RS with the salesman you will be the only person in the store that has even the vaguest idea of what you're talking about.

I'm not sure you should jump too far ahead until we know the rated current of that heater...

OK, 37 ohms, that will give you about 250mA at 9V.

I think you need to tell us why you want to regulate the voltage to this. Do you want to vary the voltage to change the temperature? There are better and more efficient ways.

Steve, did you extract that from the ebay link? I didn't see it.

I do need to be able to regulate the temperature between 110 and 130 degrees The size of these heaters work well and that is why I chose them. If there are alternatives with more or less the same dimensions I am certainly open to it

Brian, here's a good example of why you should make a concerted attempt to answer all questions and to provide as much information as possible. The Ebay heater link/information should have been posted in post #1.

Regarding temperature control: I asked you a question in this post
https://www.electronicspoint.com/voltage-regulator-problem-t263466p3.html#post1572609
but you didn't answer it. The question is important because voltage or current control will not guarantee constant temperature. As I see it (I think Steve too) we should be working on an adjustable temperature control. To accomplish this a Thermistor or solid state sensor would have to be bonded to the heater and two extra conductors would have to be routed back to the power supply/temp control. The thermistor or sensor would be used to provide temp feedback to keep the heater temp constant and what it's set to with a pot.

Once again I want to caution you. When you mess with the human body you're putting the proverbial cross-hairs on you and everything you own. If you pursue this get liability insurance and a lot of it.

Chris

 

[CDRIVE]

Sorry for double posting but I wanted to be sure this wasn't missed, so I elected to not edit my last post.

If the heater element resistance is not linear and can be plotted R vs. Temperature we can probably dispense with a Thermistor or other sensing device. We could then monitor current to determine the heater temp.

Chris

 

[KrisBlueNZ]

Chris, the eBay page says the resistance is 37 ohms, hot or cold. It's in the first paragraph under the pink heading.

 

[CDRIVE]

Chris, the eBay page says the resistance is 37 ohms, hot or cold. It's in the first paragraph under the pink heading.

Does that surprise me? I had a gut feeling that Steve saw it somewhere but old eagle eye on this end missed it.

Thanks!
Chris

 

[(*steve*)]

Given bdg's obvious lack of experience, even a simple thermostat circuit based on a comparator and thermistor may be a big ask.

And then if he's relying on RadioShack for parts, he may be very severely limited in his options.

bdg, the other issue is that you probably want heat, not temperature. By this I mean that you want to warm something up. This takes energy. If the thing is large, this heating element may never get up to the temperature you want. So, what is it that you are heating?

And what power source do you intend to use? You probably wouldn't want to use less than 6 AA cells. In fact there is a reasonable argument that you should use larger batteries. In addition to this, you need to be able to power the circuit that controls the temperature. There is a reasonable argument to power this from a separate 9V battery as that means the circuit will continue to operate as the main "heater" batteries go flat.

A really simple option is to use one of these in series with your heating element and bonded to it so that it cycles on and off around the temperature you want:

Something like this

Note that that one is 160C, way hotter than you want. I'm sure they're made in lower temperature ratings.

 

[bdg]

Given bdg's obvious lack of experience, even a simple thermostat circuit based on a comparator and thermistor may be a big ask.

And then if he's relying on RadioShack for parts, he may be very severely limited in his options.

bdg, the other issue is that you probably want heat, not temperature. By this I mean that you want to warm something up. This takes energy. If the thing is large, this heating element may never get up to the temperature you want. So, what is it that you are heating?

And what power source do you intend to use? You probably wouldn't want to use less than 6 AA cells. In fact there is a reasonable argument that you should use larger batteries. In addition to this, you need to be able to power the circuit that controls the temperature. There is a reasonable argument to power this from a separate 9V battery as that means the circuit will continue to operate as the main "heater" batteries go flat.

A really simple option is to use one of these in series with your heating element and bonded to it so that it cycles on and off around the temperature you want:

Something like this

Note that that one is 160C, way hotter than you want. I'm sure they're made in lower temperature ratings.

Hi,
I brushed liquid latex up about 20 layers in an oval about three inches wide by two inches tall. The kapton heater is placed in the center and brushed over with latex again. I cut a zip lock bag about one inch by one inch and filled it with a clay based material (like from a heating pack you would place in the microwave and heat up) and closed it with an impulse heater. A duplicate copy of liquid latex is placed on top. At 9 volts (direct from a adjustable power source) will heat up the kapton and in turn the clay heats up to the desired temp of about 110-120 degrees.

I don't have to use RS, I can order anything you guys suggest. I want to use a DC power source because I don't want any issues if the device gets wet or damp and mixes with electricity in any way. The temp also needs to be adjustable in case it gets too hot or if someone feels that it is not hot enough. I do need larger batteries (at least with the circuit I am using now). I currently need 12 in to get 9 out, but have a hard time finding the right combination of batteries. I have used 8AA but get less than 12. I have also put 2 9V together but those don't work well at all and Chris let me know that they were the bottom of the heap when it came to batteries.