Hello, I have seen in several layout guidelines that the Ethernet transformer should be placed as close to the RJ-45 connector as possible, while...

Hello, I have seen in several layout guidelines that the Ethernet transformer should be placed as close to the RJ-45 connector as possible, while the close placement of a PHY to the transformer is not as critical. Why is that? It seems counter-intuitive: I would think that the PHY should as close to the transformer as possible, while the lines between the transformer and the RJ-45 are just diff...

Hi, I'm designing a flyback transformer of a 25 W power supply. The power supply will be UL tested in Europe. The norm that will...

Hi, I'm designing a flyback transformer of a 25 W power supply. The power supply will be UL tested in Europe. The norm that will be followed is the UL 60950. The UL safety engineer told that the Hi-Pot test will be carried out after leaving the power supply in the humid room for 12 hours at 93% of humidity. He suggested me to add sleeving to the transformer. My question is: on w...

Hi, I'm looking for a source for the Halo TG43 or Valor ST7010T Ethernet isolating transformer. RS and Farnell don't supply and so does anyone...

Hi, I'm looking for a source for the Halo TG43 or Valor ST7010T Ethernet isolating transformer. RS and Farnell don't supply and so does anyone know of either a source of them or an equivalent part please. Thanks v much, Jerome

Hi, I have to write the winding specifications for a 20 Watt, flyback transformer. The core selected is an E 25/13/11. Current and...

Hi, I have to write the winding specifications for a 20 Watt, flyback transformer. The core selected is an E 25/13/11. Current and voltages calculations are ok. I have to comply to the following standards: IEC950 IEC335 IEC61558 for reinforced insulation Primary to Secondary Insulation =E2=89=A5 4000V Primary to Auxiliary Insulation =E2=89=A5 1500V I opened a couple of...

Hi all, I have a device that is powered by 240VAC (also works from 120VAC). The AC drives the primary of a transformer (with a fuse and a...

Hi all, I have a device that is powered by 240VAC (also works from 120VAC). The AC drives the primary of a transformer (with a fuse and a MOV). There is also a fan connected to the 240VAC with a switch. The secondary of the transformer has a bridge, a large electrolytic cap (1000uF/25v) and an LM7805 regulator. There is a smaller cap (10uF/10v and 01uF/25v) at the output of the LM7805. ...

I'm having a hard time figuring out exactly when its necessary to enlist the services of UL, when its might be a good idea, and when its just a...

I'm having a hard time figuring out exactly when its necessary to enlist the services of UL, when its might be a good idea, and when its just a waste of money. They are, what, a QC lab? Do they test products to UL standards, government standards, legal requirements, or what? If I create a product, say a board that runs on 5V, and that 5V comes from a UL listed wall transformer, does the pro...

Hi all, I need 5 independent power supplies. I can use a single transformer with 5 secondary windings but I haven't been able to find one...

Hi all, I need 5 independent power supplies. I can use a single transformer with 5 secondary windings but I haven't been able to find one (Vin=115vac ok). Is there a chip that can do the same ? Vout=24vdc, max Iout 20 mA (each). Thanks

is there such a beast? My ethernet circuit floats at ~ 240AC mains and I'd like to use the Ethernet transformer for Isolation. Most I have...

is there such a beast? My ethernet circuit floats at ~ 240AC mains and I'd like to use the Ethernet transformer for Isolation. Most I have seen is 1kV Or should I look else where to put my Isolation barrier. Regs Joe

Not sure if this is the right place , but: I need to power some analogue stuff from a USB port, and AFAIU the USB on the PC/MAC will limit the...

Not sure if this is the right place , but: I need to power some analogue stuff from a USB port, and AFAIU the USB on the PC/MAC will limit the current available to 100mA on connect. I think I will need about 200mA, so how do I "simply" inform the source to let me have it? This is mainly to power a transformer isolated smps +-12v for opamps, a (nonPIC) micro could be powered from the USB ...

In most DIY stores you can find these cheap Chinese digital timers to turn you lamps or appliances on at specified time. The thing I'm wondering...

In most DIY stores you can find these cheap Chinese digital timers to turn you lamps or appliances on at specified time. The thing I'm wondering is, how do they power the digital circuitry from 110VAC in a device costing only $5-$10? Are they using a transformer or are they directly powering the digital circuitry from the AC voltage?

I am designing a project that is very similar to TI MSP-WDS430BT2000D kit. My design would need rechargeable battery, be Water-resistant and to...

I am designing a project that is very similar to TI MSP-WDS430BT2000D kit. My design would need rechargeable battery, be Water-resistant and to have some way to talk to external world without opening it, and be rugged to external enviroment (shower, swiming poll and so on). The current version is using a push-pull transformer in order to create a isolated interface to recharge the battery and iRDA...

Have have an interesting problem. I need to transfer power (7V @ 20mA approx. 140mW) across a 2-3 inch air gap without using a wire. It...

Have have an interesting problem. I need to transfer power (7V @ 20mA approx. 140mW) across a 2-3 inch air gap without using a wire. It will be in a high vibration and dirty (ie. greasy, oilly) evironment. Here are my ideas: 1) create an air gap transformer 2) use super bright LED's and a Solar panel Does any one have any experience or knowledge in this area that could offer s...

I am doing some preliminary "back of the envelope" design work on a high-end split phase / three phase 50 Hz. to 400 Hz. AC power supply...

I am doing some preliminary "back of the envelope" design work on a high-end split phase / three phase 50 Hz. to 400 Hz. AC power supply & analyzer. Advice/comments/ridicule/brickbats welcome... Generating the 2 or 3 phases is straightforward, but monitoring the current and voltage is a bit more tricky -- especially when monitoring the far end of a transformer, line filter, or pow...

Hi everybody, I have a project to build 14V/3A adaptor to drive an LCD monitor. the block diagram can be described as follow: main plug...

Hi everybody, I have a project to build 14V/3A adaptor to drive an LCD monitor. the block diagram can be described as follow: main plug (220VAC) --> step down transformer (18VAC) --> diode bridge using 1N5402 --> cap 4700uF/25V --> voltage regulator LM350T --> Voltage Divider --> DC Jack Using my DMM, I measure the unloaded output voltage is 20VDC. After I load the adaptor with rhe LC

What kind of electrical signal is involved with the spark plug? I know the voltage is amplified with a induction coil to thousands of volts, but...

What kind of electrical signal is involved with the spark plug? I know the voltage is amplified with a induction coil to thousands of volts, but is the signal just a simple pulse? What kind of current is there? Does the current create the spark and then return through the same cable? I just hooked a split core current transformer with 3000 windings around a spark plug cable and got nothing. I'm...