Light Therapy

[blackchisel97]

Did some more tests today.

Tried a nte2396 mosfet instead of the irf510. The 2396 solved the current issue but I noticed that at 4672hz the current doesn't start to really flow until I increase the duty cycle.
I also tested this circuit without the transistor, the goal was to find the max duty cycle for each frequency that allows 350ma for the red/blue and 550ma for the IR.
I should be able to get the same light output at all of the frequencies.

What is the resistor value going to the gate/collector? Did you try lowering a bit?

Vtech

[nte]

Sorry, I only noticed this particular value now. There is something not right here. 20mA is way too low.

Vtech

Did some more tests today.

Tried a nte2396 mosfet instead of the irf510. The 2396 solved the current issue but I noticed that at 4672hz the current doesn't start to really flow until I increase the duty cycle.
I also tested this circuit without the transistor, the goal was to find the max duty cycle for each frequency that allows 350ma for the red/blue and 550ma for the IR.

I should be able to get the same light output at all of the frequencies.

[blackchisel97]

At 4672hz the current draw for the Red LED string is 20ma

Sorry, I only noticed this particular value now. There is something not right here. 20mA is way too low.

Vtech

[nte]

I have been playing with the CC Driver board trying to figure out why the current is lower then the test data I collected. It might have to do with extra resistances in the circuit.

While testing something strange happened and the current shot up to around 1000+ma. I didn't burn out any LEDs but I think I'm going to switch back to powering the lights with radiant energy.

[blackchisel97]

I hooked up one of my smaller LED panels (16W, 230LED's all 660nm) to my seven band pulser circuit and used my wife as guinea pig (hope she doesn't read this), since she is way more sensitive than I. She did notice big difference in pulsed v.s steady light and also noticed different sensation between bands. We have tested lower settings from 73Hz - 292Hz. This was blind test because I didn't tell when frequency have been changed. She described having feeling of vibrational heating but not on the surface (not surprise since they're low power LED) but deeper, under the skin. This would confirm others research in this field and ability of certain wavelengths to penetrate way beyond ectodermal (outer skin) layer.
I'm aiming for 700+ LED panel (if I can afford). It will be mounted via quick plate to the tripod, allowing full adjustment and treatment of any body area. I need to modify pcb a bit to accommodate small heatsink for CC Mosfet driving stylus. This Mosfet gets warmer limiting 1W LED than the main one pulsing 16W panel but there is no need to limit panel draw.

Will update when additional progress is made.

Thanks
Vtech

[blackchisel97]

I'm using only red 660nm and the highest draw at 73Hz is 245mA. It drops to 200mA at 146Hz and stays at 180 ish for all higher settings. I have a small heatsink, maybe twice the size of mosfet and it is about 50degC on highest draw. I replaced mosfet base resistor for 100k.
I'm powering from 15VDC since I'll need this for 12V panels.

Vtech

[nte]

This instructable has a little more info and good info in the comments
High Power LED Driver Circuits

My R3 Resistors and current draw at 73hz:
Blue - 1.6ohm - 100ma
Red - 1.6ohm - 80ma
IR - .82ohm - 250ma

Rated Max Current for each 1W LED:
Red- 350ma
Blue - 350ma
IR - 550ma

At 4672hz the current draw for the Red LED string is 20ma

I'm thinking the next step is better data collection.

[blackchisel97]

With the 50% duty cycle the constant current circuit isn't providing the full current to the LEDs, the current lowers as the frequency gets higher and the brightness lowers as well.

I want to stay below the max LED rating - 300mA. The highest current flows at lowest 73Hz setting, as you said but despite being lower at higher frequencies it's still detectable as a different vibration. I meant adjusting resistor in the gate of Mosfet, not the base of transistor ( as I typed earlier). I believe R3 should be calculated from 0.7/If_LED where 0.7V is the junction drop (In my case 2.8Ohm for 0.25A) not 0.5.

Thanks
Vtech

[nte]

Hi nte. Good job on your pulser. I like it.
The reason behind smaller LED is that I want to create sort of a light pad which can be applied over an area such as joint, muscle, lower back or chest and will provide a uniform field. I can feel the pulse difference even with 1W stylus so it isn't the power of unit but correct spectrum and frequency. Of course, it will be much less trouble using 1W LED matrix instead of small, 5mm ones and I'm still debating. One thing to consider is the life expectancy of small vs power LED's. These small ones will last long time since they're rated at 50,000 - 100,000hrs of continuous use. Also, two such units could be strapped on both sides of troubled ankle or a knee and penetrate the entire area. There is also a difference in projection angle in different LED's. Narrow field, such as 20-30deg will require placing them close together while wide field allows more distance in between. The one I have in stylus is 40deg but this is designed for treatment of small area.
I decided to put CC circuit on my stylus to divert the heat from resistor into mosftet. These simple circuits are linear and not very efficient but we're not talking tens of watts being wasted. I may need to readjust the base resistance a bit. I have 10k right now. I used 2N2222 and IRF640 (what I have on hand atm).

Thanks for sharing your work

Vtech

I too have noticed the importance of the correct frequencies and spectrums.

With the 50% duty cycle the constant current circuit isn't providing the full current to the LEDs, the current lowers as the frequency gets higher and the brightness lowers as well.
My small light with fixed resistors increases brightness as the frequency rises.

In the video the light has 60deg lens on each led, I also have 15,30 and 45 deg lens that I can switch.

Here is some good info on the constant current source circuit:
Power LED's - simplest light with constant-current circuit

selecting R3:

The circuit is a constant-current source, the value of R3 sets the current.

Calculations:
- LED current is set by R3, it is approximately equal to: 0.5 / R3
- R3 power: the power dissipated by the resistor is approximately: 0.25 / R3

I set the LED current to 225mA by using R3 of 2.2 ohms. R3 power is 0.1 watt, so a standard 1/4 watt resistor is fine.

[blackchisel97]

Hi nte. Good job on your pulser. I like it.
The reason behind smaller LED is that I want to create sort of a light pad which can be applied over an area such as joint, muscle, lower back or chest and will provide a uniform field. I can feel the pulse difference even with 1W stylus so it isn't the power of unit but correct spectrum and frequency. Of course, it will be much less trouble using 1W LED matrix instead of small, 5mm ones and I'm still debating. One thing to consider is the life expectancy of small vs power LED's. These small ones will last long time since they're rated at 50,000 - 100,000hrs of continuous use. Also, two such units could be strapped on both sides of troubled ankle or a knee and penetrate the entire area. There is also a difference in projection angle in different LED's. Narrow field, such as 20-30deg will require placing them close together while wide field allows more distance in between. The one I have in stylus is 40deg but this is designed for treatment of small area.
I decided to put CC circuit on my stylus to divert the heat from resistor into mosftet. These simple circuits are linear and not very efficient but we're not talking tens of watts being wasted. I may need to readjust the base resistance a bit. I have 10k right now. I used 2N2222 and IRF640 (what I have on hand atm).

Thanks for sharing your work

Vtech

[nte]

Worked on the light device today, here is a quick update:

[nte]

Nice work nte. Good idea with CC driver.
I've been working today on pcb for my RLT pulser and finally got it done, just now. This is the same circuit as I posted earlier, built on IC 4047. Since my frequency meter runs on 5VDC I decided to use 7805 to power my entire board. 4047 runs from as low as 3V. Board is about 50mmx40mm and accommodates 4047, 7805 Mosfet with small heatsink as well as rotary switch with seven 1k trimpots. Since this is 50% duty cycle pulse I didn't bother with constant current limiter. I only have 3W limiting resistor inside the stylus. I tested both, stylus and 16W 660nm LED panel while powering from 15VDC and there is no problem running at 4kHz setting. My panel has limiting resistors for branched LED's and they are calculated for 12V constant input. I'm planning to have an option of using stylus with 1W LED as well as one or two custom built units of 120-150 LED's each.
I still need to design those LED boards and find suitable enclosure for both, unit and light panels. It is gonna be fun soldering them...300 points...side by side...

Thanks
Vtech

Looking forward to seeing it!

Not wanting to solder 300 points side by side is why I switched to the bigger LEDs

[blackchisel97]

Finally built the driver board for the 13watt light.

Nice work nte. Good idea with CC driver.
I've been working today on pcb for my RLT pulser and finally got it done, just now. This is the same circuit as I posted earlier, built on IC 4047. Since my frequency meter runs on 5VDC I decided to use 7805 to power my entire board. 4047 runs from as low as 3V. Board is about 50mmx40mm and accommodates 4047, 7805 Mosfet with small heatsink as well as rotary switch with seven 1k trimpots. Since this is 50% duty cycle pulse I didn't bother with constant current limiter. I only have 3W limiting resistor inside the stylus. I tested both, stylus and 16W 660nm LED panel while powering from 15VDC and there is no problem running at 4kHz setting. My panel has limiting resistors for branched LED's and they are calculated for 12V constant input. I'm planning to have an option of using stylus with 1W LED as well as one or two custom built units of 120-150 LED's each.
I still need to design those LED boards and find suitable enclosure for both, unit and light panels. It is gonna be fun soldering them...300 points...side by side...

Thanks
Vtech

[nte]

Finally built the driver board for the 13watt light.

The board has three of these circuits on it with an input for each spectrum.




The light(now with heat sinks)


Testing




Short video of the circuit with a micro controller providing a single signal to all three channels. I noticed that the different color LEDs were seemed to be taking turns pulsing so I slowed it down to about 4hz to investigate.

!!!!! WARNING BRIGHT LOW FREQUENCY FLASHING !!!!!

[blackchisel97]

Just an update to my version of Red Light Pulser. I just received a frequency panel meter (the third one) and it works fine with my circuit. The previous ones were accurate down to 2.5Hz which is ridiculous if we're aiming at 1Hz precision.
Here is a link - http://www.ebay.ca/itm/261152194791?...84.m1497.l2649 It is only $9 but worth the money. It operates on 5V so I had to put another Zener diode. Main power supply is 15VDC and reduced down to 12V for timer chip. I decided to use 1k 10T trimpots for precise tuning of each setting. Too much work playing with 3-4 resistors in series. Now I just need to find enclosure, finish light pens, make portable LED panel units and design pcb. Almost there

Thanks
Vtech