Use for the Tesla Switch

[Matthew Jones]

Matt,

Having never used a microprocessor before, I am a little confused as to what to do to connect up to the Basic Stamp homework board.

You said in your instructions to look at the program for lighting a light bulb. The tutorial for turning an LED on and off says take a jumper from the pin 1 IO port on the left of the Homework Board to any row on the breadboard. Connect a resistor between that row and any other row. Now connect the light between this new row and ground at Vss. The idea being that the IO port would be supplied with power on command which would then go through the resistor, through the LED and to ground, lighting the light. The key being that the pin 1 IO port receives the voltage on command.

I figured that to connect up, all I would have to do is connect to the pin 1 IO port with my wire to receive power since power is all I am looking for as the other side of the circuit is a common ground since the Stamp is powered off the 12 volt battery. Is there a flaw in my logic?

Anyway, it is almost 4:00 AM and I'm calling it a night. I had hoped to fire this thing up tonight, but right now my brain is fried from trying to figure this out. I don't have any idea what I am doing wrong, but I can't get that 24 volt reading when the two batteries are supposed to be in series, and I have checked all my connections. Not once or twice, but a bunch of times. I have disconnected the transformer 12 volt wires, but left the AC side connected as that shouldn't impact anything.

In only ONE of the drawings are the batteries numbered, but I am assuming the numbering of the batteries is the same on all of them. If not, that could be my problem. I built the simple relay circuit. I have the other two circuits built also, but wanted to run this one first.

First thing I will do in the morning is put my meter between pin 1 IO port and ground and run the program and see if I have power going on and off. I'm not in the shop now, or I would do that. Oh wait, it IS morning! Should have done that before I began this mumbling.

David

If your using the home work board and you wanna drive relays. You just pull a connection from a pin out to the Positive Low voltage ON. The bring another connection back from the Negative low voltage On to the ground pin on the stamp.

Its pretty simple, as long you know where everything is.

I do not have a homework board any more I would take picture. Basically you replace the LED in the tutorial with the Relay and forget about the resistor.

Matt

[nvisser]

Hi All
I build a mosfet switch according to Matt’s idea and started testing it this morning. I used a 12-12V to 240V 50Hz, 3A transformer and pulse it with 50 Hz. The output is about 220V and I drive an 11W 240V unmodified bulb with it. The 4 batteries I use are 12v, 4AH. So the load draws about 1A from 12V which may be a bit above the C20 rate. I am not sure how to calculate it on this configuration.
It has been running for 8 hours now. The top batteries are still above 13V and the 2 bottom ones are now starting to go below 12V.
I think I will swap top and bottom batteries when the bottom ones reach around 11.5V and see how much more I can push out of this system.
The switch uses 4 Mosfets in parallel on each side and the run cold with this load.
I am not sure how to test the 4 batteries in parallel to this load to see how it compares. Maybe I will run it through a tiny inverter I have and drive the bulb from it.
I already disassembled the transformer once to split the centre tap so maybe next week sometime I will do it again and rewire the secondary for 14V and retest.
I use a small 8M picaxe with this simple code to get 50Hz.

main: high 1
pause 9
low 1
pause 0
high 2
pause 9
low 2
pause 0
goto main

[Bit's-n-Bytes]

Hi All
I build a mosfet switch according to Matt’s idea and started testing it this morning. I used a 12-12V to 240V 50Hz, 3A transformer and pulse it with 50 Hz. The output is about 220V and I drive an 11W 240V unmodified bulb with it. The 4 batteries I use are 12v, 4AH. So the load draws about 1A from 12V which may be a bit above the C20 rate. I am not sure how to calculate it on this configuration.
It has been running for 8 hours now. The top batteries are still above 13V and the 2 bottom ones are now starting to go below 12V.
I think I will swap top and bottom batteries when the bottom ones reach around 11.5V and see how much more I can push out of this system.
The switch uses 4 Mosfets in parallel on each side and the run cold with this load.
I am not sure how to test the 4 batteries in parallel to this load to see how it compares. Maybe I will run it through a tiny inverter I have and drive the bulb from it.
I already disassembled the transformer once to split the centre tap so maybe next week sometime I will do it again and rewire the secondary for 14V and retest.
I use a small 8M picaxe with this simple code to get 50Hz.

main: high 1
pause 9
low 1
pause 0
high 2
pause 9
low 2
pause 0
goto main

Very nice work Vissie!

Jeff

[Turion]

Matt,

Here is my confusion. I hooked a meter with the positive on Pin 1 out on the Homework Board and the Neg on battery 3. It reads nothing.
I type in the following code:

Do
High 1
Loop

When I do this I get a voltage reading on the meter which indicates that I now have power to Pin 1. Shouldn't that be all I need to do? Since the Board is powered by battery 3 the ground connection on the board is the ground of battery 3. The relay is getting its ground from its direct connection to battery three, which is also where the Homework board gets its ground. All those grounds are connected.

By the way, in the first test of your test guide you indicate putting your meter on two points to see if the batteries are serialized. The neg of battery 3 to the neg of battery 4. I THINK it should be from the pos of battery 3 to the neg of battery 4. Believe me, I am not trying to be picky. I followed your instructions exactly as they are written because WHAT DO I KNOW!!! Unfortunately, I get no voltage reading either way. ZIp, Zilch, Nada.

I checked every single one of my connections again and discovered I had wired in the two bottom diodes according to what the picture looked like and NOT according to the SYMBOLS on the picture, so of course the bottom two diodes were backwards and had to be rewired. But that is now fixed.

David

[Matthew Jones]

Matt,

Here is my confusion. I hooked a meter with the positive on Pin 1 out on the Homework Board and the Neg on battery 3. It reads nothing.
I type in the following code:

Do
High 1
Loop

When I do this I get a voltage reading on the meter which indicates that I now have power to Pin 1. Shouldn't that be all I need to do? Since the Board is powered by battery 3 the ground connection on the board is the ground of battery 3. The relay is getting its ground from its direct connection to battery three, which is also where the Homework board gets its ground. All those grounds are connected.

By the way, in the first test of your test guide you indicate putting your meter on two points to see if the batteries are serialized. The neg of battery 3 to the neg of battery 4. I THINK it should be from the pos of battery 3 to the neg of battery 4. Believe me, I am not trying to be picky. I followed your instructions exactly as they are written because WHAT DO I KNOW!!! Unfortunately, I get no voltage reading either way. ZIp, Zilch, Nada.

I checked every single one of my connections again and discovered I had wired in the two bottom diodes according to what the picture looked like and NOT according to the SYMBOLS on the picture, so of course the bottom two diodes were backwards and had to be rewired. But that is now fixed.

David

Ya you can ground to Batt3 or to the stampboard same thing.

Your right I have that diagram screwed up. Check from the positive of Batt3 to the negative of Batt 4. You should have 24 volt +-

I'll fix that diagram.

Matt

[Turion]

Matt, just to let you know I got it up and running. At least to the point of completing all the tests to see if everything is working. If it doesn't work when I fire it up at this point, it's because I didn't label my transformer wires correctly, so shame on me if that happens. Both relays were definitely blown, so using the 1000 ohm resistor solved the problem second time around. It fired right up.

The drawing for the relay version shows the side of the relay that does not have the metal on it as the top of the relay. This is ok for the relay on the left, where it shows the stamp connected to pin 4 (if you go bottom to top with pin 1 on the bottom and pin 4 on the top) But to wire the relay on the right correctly (IE pin 4 going to the stamp) you would have to flip that relay over with the metal side up to get pin 4 on the top where it is connected to the stamp. At least that is the way I see it. If I'm wrong, it wouldn't be the first time.

I didn't understand how a relay really worked until this project, and as Matt has told me more than once READ the data sheet! I wired mine wrong and didn't catch my mistake until I was talking to Matt on the phone. I just arranged my relays like in the picture and wired them up. Now I know better.

Thanks Matt, for all your help. Like I said before, if I can get this thing up and running, ANYBODY can! I am the perfect test case. Somebody who knows nothing, but won't quit trying.

[Matthew Jones]

Thats good to hear David. Make sure you follow the instructions as far start up and you'll get it running.

Cheers
Matt

[ren]

Hi Matt,

In regards to solidstate relays I have found some that have a switching time of 10mS or less. I believe the Hongfa's are 1mS though. Is this going to be a problem? There are DC/DC relays that go up to 80 amps and over 100vdc to pick from, but all of them are 10mS. I know you dont need to run high frequencies, but I want to check before I purchase a couple.

I finished up the "brains" last night, an Audrino board I had laying around. Gonna have a crack at the code and blink some LEDs tonight. Also found three good old school transformers laying around that I am going to split this week and rewire.

Regards

Ren

[SkyWatcher]

Hi folks, well I wound the 3 strands, though I had more 18 gauge wire than I thought and it didn't need much anyway.
I measured a strand without trimming off the 2 strands yet and 1 strand measured between .3-.4 ohms, so when I trim the 2 primary strands down 25% or so, each strand will probably be .3 ohms or lower.
I wonder if this will be too low of a coil resistance and might cause the transistors I will be using to overheat, 2n3055 NPN, I realize it's pulsed and all, though should the transistor be able to handle the peak currents and if not, could it cause unnecessary heating of the transistors.
Otherwise, I could use the 24 gauge and raise the resistance. What do you folks think, thanks.
peace love light
tyson

[SkyWatcher]

oh and based on the ohms, it looks like about 50 feet of wire per strand, then a little less when the primary strands are trimmed.

[citfta]

Hi Skywatcher,

Matt can give you a better opinion when he gets a chance to look at your post, but I think your resistance is pretty close to right. It is almost the same as my modified Radio Shack transformer. I am afraid you are going to have trouble with those transistors though unless you have some really good heat sinks for them. I am using the MJL21194 transistors and they get pretty warm even with heatsinks. All you can do is try I guess and watch the temp closely. Or wait for Matt's opinion.

Carroll

[Sobakin]

Just finished another test:
0.2A (about 2.5W) 80mm computer cooling fan.
7 hours running; then swap batteries; again 7 hours running; after that batteries was discharged.
This time I regulated transformer's output voltage (which is with small load is about 15.5V on fully charged batteries) by changing duty cycle (pulses with deadtimes between), so output voltage was 12-12.5V.

So I feel that still can't repeat Matt's good result

Maybe I need to try bigger batteries, at least 7Ah?
Next I'll test same load with my old 6-switch TS.

[ehsanco1062]

Hi Matt
I have two wire 60 feet #20AWG and thats all I have but for the longer wire I have only 21AWG and 19 AWG I dont know which one is butter to choes can you help with this or I have to wait two weeks for my order to be here?

Thanks
Ehsan

[hiops]

microoven transformer

Hi, Matt!
Do you think that microoven transformer would be good for small TS, or maybe it will be ok for the big one?
Alex

[Sobakin]

Hi, Matt!
Do you think that microoven transformer would be good for small TS, or maybe it will be ok for the big one?
Alex

Such transformer may be not iron but ferrite which is high frequency, more than 10KHz, I don't know is it good for Matt's TS, because Matt's is iron-based?