hawkmoon45
- Jan 1, 2013
- 2
- Joined
- Jan 1, 2013
- Messages
- 2
Hi Guys, having been an electrician for the last 7 years, I thought it was time I understood more about electronics, thus I am asking you guys for help.
My current situation is that I bought some purple fairy lights from Hong Kong which seemed to work on a untransformed system. The little box controlling it all had basically a bridge rectifier and 3 transistors to separate circuits and a chip which controlled the flashing sequence between them.
My idea was that I could use them to create mood lighting in my daughter’s bedroom. My first thought was to separate the 3 circuits and put 1 inside the translucent wardrobe doors, one behind the body length mirror and one behind the bed head.
I stated on the Job and was never happy – No transformer? Tested the output voltage and found it to be around 220V DC. Not Good
This is where my problems started, and maybe should have asked for your help first.
100 fairy lights – 33 per circuit
I looked on line and used a LED calculator to eventually work out that I could run them on a 24VDC power supply
The parameters I needed to enter were: -
1. Supply Voltage
2. Voltage drop across each LED
3. Desired LED current
4. How many LED’s connected
1 and 4 can be easy, but when you have no facts about the LED’s 3 is a hard one, I settled at 15 mA. 20 was recommended but I stayed on the side of caution, the different resistors I used did not seem to work any better, if I went for 20 mA.
TO THE POINT - I had no way to test the amp’s used, I had a volt meter and could see the difference between 17 and 28v by adjusting the pot on the power supply.
I have a 0 to 1 mA amp meter but it is too low to use, I tried it.
I know that I can use shunt resistors to view many scales using this amp meter:-
0 to 1 mA MU 45 Class 2.5
I would like to think I have a test bed in future and be able to look at what the voltage is and what the circuit current is, it would make it so much easier.
Questions
1. Can I buy standard shunt resistors for this?
2. Can I make my own? I have 0.8. 0.56, 0.4, & 0.315mm insulated transformer wire in 500g rolls. (I would expect to test up to maximum 2A)
3. How do LED relate to resistance?
I would be Greateful for any advice
Hawkmoon
My current situation is that I bought some purple fairy lights from Hong Kong which seemed to work on a untransformed system. The little box controlling it all had basically a bridge rectifier and 3 transistors to separate circuits and a chip which controlled the flashing sequence between them.
My idea was that I could use them to create mood lighting in my daughter’s bedroom. My first thought was to separate the 3 circuits and put 1 inside the translucent wardrobe doors, one behind the body length mirror and one behind the bed head.
I stated on the Job and was never happy – No transformer? Tested the output voltage and found it to be around 220V DC. Not Good
This is where my problems started, and maybe should have asked for your help first.
100 fairy lights – 33 per circuit
I looked on line and used a LED calculator to eventually work out that I could run them on a 24VDC power supply
The parameters I needed to enter were: -
1. Supply Voltage
2. Voltage drop across each LED
3. Desired LED current
4. How many LED’s connected
1 and 4 can be easy, but when you have no facts about the LED’s 3 is a hard one, I settled at 15 mA. 20 was recommended but I stayed on the side of caution, the different resistors I used did not seem to work any better, if I went for 20 mA.
TO THE POINT - I had no way to test the amp’s used, I had a volt meter and could see the difference between 17 and 28v by adjusting the pot on the power supply.
I have a 0 to 1 mA amp meter but it is too low to use, I tried it.
I know that I can use shunt resistors to view many scales using this amp meter:-
0 to 1 mA MU 45 Class 2.5
I would like to think I have a test bed in future and be able to look at what the voltage is and what the circuit current is, it would make it so much easier.
Questions
1. Can I buy standard shunt resistors for this?
2. Can I make my own? I have 0.8. 0.56, 0.4, & 0.315mm insulated transformer wire in 500g rolls. (I would expect to test up to maximum 2A)
3. How do LED relate to resistance?
I would be Greateful for any advice
Hawkmoon