Breadboard voltage limits?

[FusionITR]

I plan on building a offline boost converter on a breadboard before manufacturing a pcb for it. Mains voltage will be into the pcb and the output voltage will be 230V. Does this beyond the breakdown voltage limits of a standard breadboard? Serious question, not a troll, I have never built anything this high voltage on a breadboard.

 

[ericgibbs]

I plan on building a offline boost converter on a breadboard before manufacturing a pcb for it. Mains voltage will be into the pcb and the output voltage will be 230V. Does this beyond the breakdown voltage limits of a standard breadboard? Serious question, not a troll, I have never built anything this high voltage on a breadboard.

Hi,
Look here. https://www.google.co.uk/search?q=b...s=org.mozilla:en-GB:official&client=firefox-a

 

[Mikebits]

What I would be worried about is the switching currents. Most typical SMPS pcb's have large ground planes to mitigate problems associated with switching currents and noise. A breadboard will give you poor grounding and may result in erratic operation.

 

[crutschow]

I suggest you build it on a breadboard with a copper ground plane, such as this, to minimize the problem that Mike noted. Use the plane for all ground connections.

If bringing 220V on the board, allow space around all 220V connections (noting connected to adjacent pads) to help the isolation.

And please use a 220V isolation transformer for added safety when working with 220. 220V is dangerous by itself without exposing yourself to possible ground fault electrocution from the 220 mains.

 

[FusionITR]

I suggest you build it on a breadboard with a copper ground plane, such as this, to minimize the problem that Mike noted. Use the plane for all ground connections.

If bringing 220V on the board, allow space around all 220V connections (noting connected to adjacent pads) to help the isolation.

And please use a 220V isolation transformer for added safety when working with 220. 220V is dangerous by itself without exposing yourself to possible ground fault electrocution from the 220 mains.

I'm working with 120 mains (I'm in the US) but thanks for the suggestion I'll see if they have this type of breadboard at frys.

And yes, I am using a isolation transformer in the form of a variable AC power supply with current limiting (**broken link removed**). I'm going to try to be as safe as possible but I really do need to breadboard this before I spent a few hundred dollars and a few days of my time doing a pcb layout for this. First time building a boost converter and I'm not confident it will work without testing.

 

[ronsimpson]

I do large 220/110 AC to 400VDC supplies on bread boards.
For ground and heavy current areas I use copper tape to make wide traces and ground planes.
Watch you spacings.

 

[FusionITR]

I do large 220/110 AC to 400VDC supplies on bread boards.
For ground and heavy current areas I use copper tape to make wide traces and ground planes.
Watch you spacings.

What safety procedures do you recommend?

 

[ronsimpson]

It sounds like you are going from 110ac to 230 v dc.
When I make a switching power supply, (power line to DC), I start off not using the power line. I use a DC bench supply with current limit. 150 volts 1 A supply The power line does not have good current limit! Then things are working well I switch to power line throught a isolation transformer (which has a current and voltage meter). I have a box that isolates and allow me to dial in the voltage from 0 to 150 volts ac.

 

[FusionITR]

It sounds like you are going from 110ac to 230 v dc.
When I make a switching power supply, (power line to DC), I start off not using the power line. I use a DC bench supply with current limit. 150 volts 1 A supply The power line does not have good current limit! Then things are working well I switch to power line throught a isolation transformer (which has a current and voltage meter). I have a box that isolates and allow me to dial in the voltage from 0 to 150 volts ac.

Yes I am going from 110ac to 230vdc. Then from that I plan to build 230vdc to 5vdc/12vdc/-5vdc using a flyback/buck topology.

Anyhow, I am not using the power line, I am using the isolation transformer with current limit, the one I posted above. I am also using a varistor to tame the inrush current. Any other suggestions?

 

[crutschow]

Is that variable AC transformer a Variac type device? If so, it is not isolated. The input and output have a common connection.

 

[FusionITR]

Is that variable AC transformer a Variac type device? If so, it is not isolated. The input and output have a common connection.

It says "Isolated 2A" in the picture.

 

[RichTheDude]

Surprises me if a variac has isolation, I thought they was basically auto transformes. I guess it could have an isolation transformer inside it somehere too.

 

[crutschow]

It says "Isolated 2A" in the picture.

Yes, it is not a variac. It appears to be a AC supply with an isolated output.

 

[KeepItSimpleStupid]

Instrumentation (0-120 VAC) sold for servicing stuff will typically be isolated. It may also include a leakage tester.

 

[Dean Huster]

The instruction sheet that comes with decent breadboards (Global Specialties or E&L, both owned by Interplex Electronics) will have the voltage ratings for their contacts. You can bet that the Asian imports won't -- and they don't work as well or have the LIFETIME UNLIMITED WARRANTY that the above-mentioned products do. Although more expensive, the warranty makes those two brands worth the cost. You can melt them with overdissipated resistors or reversed ICs, use lead diameters that are so large that they spring the contacts, break off wires in the holes -- and those two companies will replace their breadboards with no questions asked ... just pay for the shipping of your busted-up breadboard to them and they'll cover the return. I've done this dozens of times with them.

As to the voltage ratings. Pull the back paper off your breadboard and you'll see that the adjacent contacts are spaced pretty closely, too close for my comfort for use at 120vac, let along 240vac ... that's 340v peak or 680v peak-to-peak, folks! What you can do is pull out every other contact on the portion of the board where you will be doing the HV wiring, marking the appropriate "blanks" on the top side. Put the paper back on and wire with more safety. Also don't forget that many of these breadboards are mounted to a metal plate with nothing more than that paper backing and a coat of paint on the metal separating two contacts. Mount the board onto a plastic base ... a polyethelyne cutting board (BREADBOARD!!) will work nicely and is available at most grocery and general stores such as Wal-Mart.

 

[squishy36]

It says "Isolated 2A" in the picture.

FusionITR: just to be safe, open the thing up and verify that it actually has an isolation transformer. The knob probably turns a Variac. B&K's latest model is the 1655A and it uses a Variac to adjust the voltage and feed it to an isolation transformer. I'd be surprised if the one you have isn't the same design.

 

[FusionITR]

Just incase you guys are curious:

**broken link removed**

It works, sorta, I get 230VDC out but there is a lot of emi noise, probably because it's on a breadboard, there is no feedback compensation, and I think the pwm is only on intermiently because auxilery power supply doesn't work as expected.

I can power up the ic fine from a benchtop power supply though. I have to work and see what is going on. I'll make a seperate thread for it.