Project Power Supply
Alexander (Sandy) Hapgood
Posts: 360
Just received a Texas Instruments PTB78560C DC/DC Converter from DigiKey. It has a very wide input voltage range ( 18 to 60 VDC ) and a 30 watt total output. Using it and two caps I have a stable project power supply with a very wide input voltage range. The input, for my application, usually runs around 28 volts but can spike to over 30 volts on occasion.
Some might find the price quite steep at $60 Canadian each but they're perfect for what I'm doing. One odd thing is the pin spacing; 1/8" and 1/4" centres instead of the usual .1" centres. Definitely not breadboard friendly.
Sandy
Some might find the price quite steep at $60 Canadian each but they're perfect for what I'm doing. One odd thing is the pin spacing; 1/8" and 1/4" centres instead of the usual .1" centres. Definitely not breadboard friendly.
Sandy
Comments
It can output 2 amps, take a wide input range -- 3VDC -35 VDC and a wide range of output from 1.25VDC to 30 VDC, but seems to be only a step down.
very similar to this ===> http://www.ebay.com/itm/LM2596-DC-DC-Step-Down-Adjustable-Power-Supply-Module-2A-/390877509680?pt=LH_DefaultDomain_0&hash=item5b021d7830
The step-up is more expensive, but still a good deal
see here ===> http://www.ebay.com/itm/350945710394
Some others don't care - can go up or down -- even come with a LED voltage readout and 3 amp output..
Here is a handy little 3 amp one ==> http://www.ebay.com/itm/4-75-24V-to-0-92-15V-Boost-Buck-Voltage-Step-Up-Down-Converter-Regulator-/301034587274?pt=LH_DefaultDomain_0&hash=item46170f448a
$60USD is a bit steep. Hopefully there is some added value that I missed seeing... maybe you need that 60VDC input range.
What these mean to me is that I can just about plug in any battery or wall wart I have and get the target output I need for a project. No more trying to figure out which battery or wall wart is required for a project.
I have bins full of battery holders for 2, 4, and 6 AA cells, Lithium cells, various voltage wall warts, and various linear regulators. A heck of a lot of that can just be set aside now.
Yes, it was the 60 VDC input that drew me to this unit. Gives me a healthy margin and the $60 is insignificant in the scheme of things, at least in the scheme of things in my world.
Sandy
In my case, the tiny step-down that is charging my Lead Acid gel cell was not only cheap, it seems to have a 92% efficiency and runs quite cool. If I had used an LM317, it would have run hot and had about 70% efficiency.
The world keeps changing.. new gadgets and new bargains all the time.
In addition to the power supply, I'm also using Crydom CMX100D10 Solid State Relays to drive solenoids, Grayhill 70M-IDC5 for optical isolation of operator input and three Crouzet Solid State Relays to drive the 7.5 HP, 3 phase, AC motor that runs the hydraulic pump..
Given that revenues are running well over $3,000 per hour ( $50 per minute ) the cost of the power supply, relays and optical isolation is insignificant if it can increase the reliability of the complete unit.
It has been an interesting project and I've learned a lot.
Sandy
We tend to have a lot of newcomers that are on a tight budget and turn to EBay for a bargain.
Power MOSfets just seem to be getting better and better. With that, the linear regulators are becoming dinosaurs as the new switching regulators run very cool instead of hot. Running 7805 regulators at 28 volts is a bit crazy. About the only reason they work is that they don't seem to have thermal shutdown, which later voltage regulators included.
Nearly everything I have seen in DC-DC converters will handle about 30VDC maximum input. But it there is the possibility of line transients causing damage, and for line transients having something that will take 60VDC without failure is likely to last much longer. Zeners and other devices can take any remaining transient over the 60VDC, but that margin will disipate a lot of the transisent's power.
In automotive circuits, I tend to look for transistors and regulators that might even handle 100VDC.. even though it is supposed a mere 12VDC circuit. There are just too many inductive loads and sudden switching on and off of heavy loads to be comfortable with something less.
They also have 3.6-5.5v (ptb778560a) and 1.8-3.6v (ptb78560b) parts.
http://www.ti.com/product/ptb78560c/samplebuy
Some companies will deliver free samples overseas if I provide a credit card for the shipping. But when you get a $40 Fed-Ex bill for a few free ICs, it hurts. And I might have to argue with the local customs agents that the samples are free and I shouldn't have to pay duty on the shipping.
Living in the USA offers a lot of sweet perks that overseas residents just can't get... like Amazon and EBay free shipping as well.
Having lived and worked in quite a few different places in the world I now know that, in North America, we do shopping better than an other place on earth. Just try to buy a sheet of plywood in Europe. I only ever saw one sheet and that was as it disappeared into a house that was being renovated on Malta!
I've been testing the power supply for a couple of days now using a 24 VDC wall adaptor. I've got a steady 8.963 to 8.967 volts going into one of my prop development boards using just the minimal setup of a 110 uF cap across the input and a 220 uF cap across the output. Everything, including the regulators on the PPDB, is running cool to the touch.
The 8.963 to 8.967 volts I measured at the output may not be very accurate as my meter hasn't had its calibration checked for quite a while now.
One of the things that worried me about using a switching power supply was the effect any ripple might have on the readings from the 12 bit ADCs I'm using. There doesn't seem to be any so it's all good.
Sandy
I have no doubt that The States is king of shopping but I don't get this: "Just try to buy a sheet of plywood in Europe".
What? Just go to the timber yard and get some. There is an awful lot of Baltic Birch around here. Admittedly I don't know how much of it makes it's way down to Malta.
Our mechanic's tool kit got dropped in the ocean just off the north coast of Egypt ( it's a long story haha ). We didn't have time to wait for replacements to come from the US so we had to purchase tools locally. I ended up at a small store in Augusta Bay, Sicily that looked, from the outside, like it might not have anything I needed. I didn't speak Italian and the guy at the store didn't speak English so I drew pictures of the tools I needed and he disappeared into the back and came back with the tools. Fortunately I needed metric tools. If I had been looking for standard wrenches I'm quite sure I would have been out of luck but it was amazing the tool selection he had. There was no indication by looking at the front of the store. Got nearly everything I needed from that one store.
I did come upon a fully stocked Snap-On tool store in Lisbon, Portugal. As far as I know Snap-On stuff is only available from Snap-On trucks in North America. Very strange.
There, I think this thread has jumped the tracks nicely.
Sandy
I have used these. http://www.murata-ps.com/data/meters/dms-78xxsr.pdf
Sandy