I need to lower 24V to 12V at 1A for 60 devices, automotive, due Wednesday - Page 1
Forum section: electronics / projects

author: ivan747
author_rank: Super Contributor
timestamp: February 10, 2018, 12:08:10 am
content: Hi,I was urgently approached for a project where I will need to power a ready-made device that takes a 12V 1A input from a 24V vehicle (update: I actually measured 0.25A in a lab setting). I need to provide a working, solution by Tuesday for testing (today is Friday). On Wednesday I'll need to install 60 units on 20 vehicles (I said 60 vehicles in the title because I preferred to be brief).Due to time constraints I am limited to the local market... which is a killer.I foundthat I have 5 options for the power conversion:* Find 20 24VDC to 120VAC inverters in the local market at a very reasonable price. That's a stretch.* Find 60 step down DC-DC converters in the local market. I research a little bit but it's not looking good. I really hope I can find these.* Using 60 voltage regulators, 7812 type. I would also need to purchase heat sinks.* Persuade them into paying for international shipping with exceptional speed, (for which time is running out and there are big consequences if it arrives late).* Miraculously find a 12V line on the vehicle. I'm not even sure if the vehicles are of the same model.These devices are supposed to go inside the vehicles. The vehicles are for public use, so the project must be enclosed. It is an RF project in the 2.4GHz band, so I can't use a metal enclosure. This worries me if I am to use 7812 regulators.It's starting to look like 7812 regulators are my only choice. How would you approach such a design? Yes, I know it's a very basic design electrically. I'm talking more about the physical constraints taking into account that:* The enclosure cannot be made out of metal due to RF issues.* The device will be within the public's reach* The 7812 will disspate 12W, nominally. In reallity the voltage on the vehicle will be around 27V.I know the 7812 is not the proper regulator for automotive use, but sorry, it's what I have available.Hope to hear your opinions! I'm more or less screwed I think...Cheers,Ivan

author: Bendba
author_rank: Regular Contributor
timestamp: February 10, 2018, 12:18:09 am
content: 555 timer, transistor and capacitors shouldn't be hard to find.Maybe you could go with a switched capacitor dc-dc converter. Not very efficient but at least you wouldn't need to dissipate 12W+

author: ez24
author_rank: Super Contributor
timestamp: February 10, 2018, 12:18:12 am
content: Just a long shot because I am sure you looked into this but can you tap into the battery somewhere? I never heard of a 24v car battery, even 48v golf carts are 6v in series. A nail (brad) and alligator clip?Surprised that you can get some of the items you talk about.Good luck

author: viperidae
author_rank: Frequent Contributor
timestamp: February 10, 2018, 12:20:34 am
content: You could start by telling us where your local market is.Local for au/NZ there ishttps://www.jaycar.co.nz/24v-to-12v-dc-voltage-converter-module/p/AA0238These kinds of things should be reasonably common

author: ivan747
author_rank: Super Contributor
timestamp: February 10, 2018, 12:25:15 am
content: Quote from: ez24 on February 10, 2018, 12:18:12 amGreat, I'll talk to whatever mechanic I can find on-site on Monday.

author: Benta
author_rank: Super Contributor
timestamp: February 10, 2018, 12:25:58 am
content: Local market seems to be Dominican Republic.OP, don't panic. Your application sounds like something for trucks or buses. They almost always have two 12 V batteries in series for 24 V. You can tap into those with no problems.Good luck.

author: ivan747
author_rank: Super Contributor
timestamp: February 10, 2018, 12:26:54 am
content: Quote from: viperidae on February 10, 2018, 12:20:34 amMy local market is the 30 de Marzo street, Santo Domingo, Dominican Republic.I could order online but it's very very risky. If it arrives late I'm screwed.Quote from: Benta on February 10, 2018, 12:25:58 amHopefully! Yeah, I'm in a sort of panic...Yes, it's for buses.

author: ez24
author_rank: Super Contributor
timestamp: February 10, 2018, 12:27:21 am
content: Quote from: viperidae on February 10, 2018, 12:20:34 amThe OP's flag says Dominican Republic - which surprised me.OP - Do schools in Dominican Republic teach electronics?

author: ivan747
author_rank: Super Contributor
timestamp: February 10, 2018, 12:34:09 am
content: Quote from: ez24 on February 10, 2018, 12:27:21 amWe have a handful of polytechnic high schools, a couple of community colleges (technic) and about 5 universities (engineering) teaching electronics. A typical class at my uni is 15 students.It's mostly a technician's profession. There's not a lot of electronics design, but there is a lot of repair and some electro-mechanical maintenance.What keeps the market alive is audio repair and power electronics (AC inverters and backup generators).

author: ivan747
author_rank: Super Contributor
timestamp: February 10, 2018, 01:13:20 am
content: How much I wish I had 60 of these... eBoot 6 Pack LM2596 DC to DC Buck Converter 3.0-40V to 1.5-35V Power Supply Step Down Modulehttps://www.amazon.com/dp/B01GJ0SC2C/ref=cm_sw_r_cp_api_X9IFAbG45TM77Sent from my iPhone using Tapatalk

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 10, 2018, 01:16:47 am
content: Find something similar that's available on Prime?

author: ivan747
author_rank: Super Contributor
timestamp: February 10, 2018, 02:05:45 am
content: Quote from: NiHaoMike on February 10, 2018, 01:16:47 amI asked the guys about it, we'll see.I am worried that these will introduce too much RF interference, though. Hopefully they won't. The product is very well shielded against radiated RFI, but I don't know how well would it deal with conducted RFI.

author: nuno
author_rank: Frequent Contributor
timestamp: February 10, 2018, 02:17:21 am
content: Quote from: Bendba on February 10, 2018, 12:18:09 amOr even a buck converter from the 555. Even if unregulated output, a 7812 could be ahead.Any microcontroller with integrated analog comparator or ADC would also be easily made into a regulated output buck converter, but there are some details on supplying the uC (5V... although low current).It's not a good idea to take power from one battery which is part of a series connected pack that has no charge equalizer... but may be one way to gain time to develop a better solution.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: February 10, 2018, 02:23:04 am
content: None of the solutions are ideal. Perhaps consider your solution to be temporary, to be replaced by a more robust solution.Dissipating 12W into a TO-220? will be trouble.Depending on the nature of the load, a series resistor before the regulator can nicely take up a bunch of the drop. For instance, a 6 ohm, 10 W resistor in series will take up half the drop, leaving the regulator to dissipate "only" 6 W. As the resistor approaches 12 ohms, you get close to dropping out the 12 V output.A 10 ohm resistor with an LDO version of the regulator would be right on the edge. Perhaps 8 or 9 ohms. Oversize the power rating of the resistor by around 2X.

author: ez24
author_rank: Super Contributor
timestamp: February 10, 2018, 02:42:53 am
content: Quote from: ivan747 on February 10, 2018, 01:13:20 amhttps://www.aliexpress.com/item/2-PCS-High-Efficiency-DC-DC-Buck-Converter-Power-Supply-Module-Step-down-Voltage-Regulator-Car/32605235844.htmlI suggest you do not get one with a pot. I believe vibrations will turn the pot. Is so glue the screw with something.Here is one without a pot and has reasonable specs (normally if a spec says 3a you can hope for 1a). Price is higher.https://www.aliexpress.com/item/High-Voltage-EBike-DC-DC-Converter-Buck-Step-Down-Regulator-Module-80V-72V-64V-60V-48V/32824239630.htmlHere is another one, sometimes easier to search on. Check out the drop down menu on the right side.https://www.fasttech.com/products/1005/10002934/6339300

author: John Heath
author_rank: Frequent Contributor
timestamp: February 10, 2018, 03:33:08 am
content: The most important question has not been addressed. Is money no object? If this is the case then there shall be an abundance of shiny new 24 V to 12 v adapters on Monday ahead of schedule.If money is an object. No way Hoe say.

author: DBecker
author_rank: Frequent Contributor
timestamp: February 10, 2018, 04:54:05 am
content: It's tough to guess what products are available in the local area.You might consider buying samples of different automotive USB power adapters and see which can modified for your requirements. Most will work at 28V, although they will not be as robust against transients at that voltage. Some designs have adjustable output voltage, while others have specialized chips with internal feedback and thus can only generate a fixed 5V output.

author: ConKbot
author_rank: Super Contributor
timestamp: February 10, 2018, 05:04:36 am
content: Have you looked at the power input section of said ready made device already? It may be able to take 24/28 vdc already, or maybe something simple like swapping 25V caps for 35/50V caps.Also try auto/truck parts suppliers, just because your vehicles don't have a separate 12v system doesn't mean others don't, and you might be able to source a 24/12V converter 'replacement' part locally. Or off the shelves for truckers to use 12v accessories.If you do end up lashing together a bunch of linear regs, go for something with a high maximum input voltage so transients are less likely to cause problems. Plus something like an LM317 has a limit on Vin-Vout rather than strictly Vin, so that is an extra 12v of headroom on the maximum input voltage. A series resistor can help spread the heat dissipation. I.e. 2 10w 5 ohm resistors in series would drop the input to the regulator to 14-18V when the load is a full 1A.

author: tautech
author_rank: Super Contributor
timestamp: February 10, 2018, 05:09:50 am
content: Nearly every automotive accessory supplier or automotive audio fit out company will have 24-12V converters.How do you think they power radios and CB's in buses/trucks ? They'reall12V devices !As you need them in a hurry, look there.The other way to 'skin this cat' is to tap off from one battery and run a new wire for your needs.Sure bit of a curse if the battery chest is at the rear.EditAdding to what ConKbot said.

author: BrianHG
author_rank: Super Contributor
timestamp: February 10, 2018, 05:10:50 am
content: Careful, for 24v vehicle, your regulator needs to withstand a good 42+v surge in case the vehicle is getting a road side boost from a tow truck which has one of those professional variable voltage hand triggered boost-starters.

author: SeanB
author_rank: Super Contributor
timestamp: February 10, 2018, 05:26:57 am
content: Common problem, go find a truck supplier and ask for 12V converter units, used so that truckers can have a 12V CB radio or whatever running off a 24V supply. They typically are a longish heatsink with a potted block in the middle, and are a pair of 2N3055 in TO220 in parallel, with a simple single transistor driver stage and a 14V zener diode and supply resistor, and a 10A diode for reverse polarity protection. Simple, rugged ( they often get driven to 20A for short periods during transmit) and likely available off the shelf.

author: Seekonk
author_rank: Super Contributor
timestamp: February 10, 2018, 07:46:50 am
content: Wednesday will pass and life will go on. I have great access to parts and I wouldn't be able to get 60 of anything in that time frame. Remember, their lack of planning is not your emergency.

author: HighVoltage
author_rank: Super Contributor
timestamp: February 10, 2018, 08:59:29 am
content: 1. Last year at a trade show here in Germany, one exhibitor was from Haiti and they built all kinds of transformers and DC/DC converters. I was surprised but the owner explained that labor cost was so low in Haiti that the business was well profitable. May be you can located them.2. Many Buses have 115 or 230V AC on board.If so, just use a AC to 12V adapter.

author: Rerouter
author_rank: Super Contributor
timestamp: February 10, 2018, 09:12:42 am
content: Quote from: ivan747 on February 10, 2018, 12:25:15 amPlease do not do this, you deplete 1 battery, which leads to overcharging the other, net result 2 dead batteries after a few weeks to a few months,Look at local suppliers for 24-12V DC-DC converters, any place that sells car radios will likely have the amount of stock you need,

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: February 10, 2018, 09:57:36 am
content: Easy peasy: put n * (1n4001 or 1n5400) diodes in a string in series, where n ~= int((24-12)/0.7)

author: Zero999
author_rank: Super Contributor
timestamp: February 10, 2018, 10:00:15 am
content: Quote from: ez24 on February 10, 2018, 02:42:53 amThe problem with those is the lead time.Quote from: ivan747 on February 10, 2018, 12:08:10 amI had a quick look on Digikey and found this. It's overkill and expensive, but is the only 24VDC:12VDC converter they have a stock of more than 60 of.https://www.digikey.com/product-detail/en/cui-inc/PQA50-D24-S12-T/102-3292-ND/4765793

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: February 10, 2018, 10:09:20 am
content: An LM320 (TO3) mounted on a heatsink can dissipate 12W much better than any 7812 (TO220). And 17 1n4001 diodes in a string even better yet.

author: nali
author_rank: Frequent Contributor
timestamp: February 10, 2018, 10:51:13 am
content: A string of diodes doesn't protect the equipment from load dump. SAE defines a load dump pulse for a 12V system as up to 125V for up to 400mS - so that's a nice juicy low impedance 250V pulse in this case. Even if the 12V equipment is designed to handle load dump it'll be rated @ 125V, not 250V minus a few diode drops.To OP - if this is for buses then expect a wide range of input voltages. Particularly if your power solution is switched mode. Buses are often left with the saloon lighting and other systems powered on and running the battery down for extended periods, the engine then takes an age to crank before it catches. The reason I mention it is it'll result in a huge swing in current draw, so be careful on your choice of fuse. I've seen the supply swing from about 6V to 30V because of this.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: February 10, 2018, 11:05:44 am
content: If his "ready-made device that takes a 12V 1A" is designed to run in a car it will surely account for all that already.

author: Yansi
author_rank: Super Contributor
timestamp: February 10, 2018, 11:13:33 am
content: Quote from: nali on February 10, 2018, 10:51:13 amThat seem like nonsense. Not a single car electronic device will survive 125V for half a second.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: February 10, 2018, 11:21:34 am
content: In any case a 100v varistor fixes that.

author: Yansi
author_rank: Super Contributor
timestamp: February 10, 2018, 11:36:41 am
content: It does only when the pulse source has rather high impedance - which you have not specified. As far as I know, automotive products for 12V system shall operate up to 42V, continuous, without damage. Not sure about 24V systems though.

author: sokoloff
author_rank: Super Contributor
timestamp: February 10, 2018, 12:48:49 pm
content: If this is a high-dollar contract, think outside the box.Catch a Saturday flight out to the states, stay in a hotel near a components distributor, order what you need for Monday delivery, test what you need to test locally there, fly back to DR on Tuesday early morning. No one glanced at my bags on the way in, but you could declare the contents easily as well.If this is not a high-dollar contract, maybe it's not actually that urgent.

author: max_torque
author_rank: Super Contributor
timestamp: February 10, 2018, 01:32:43 pm
content: How robust does this "fix" have to be and how long does it have to work for?Sounds like even if you rushed around and somehow got them all designed, built and installed in time, you'd be having them all back in a few days when the go bang!(ime, automotive "heavy" (ie buses, trucks etc) is the WORST environment possible (far, far worse than Space ime) because it's full of unskilled, untrained workers who DGAS about the thing they are operating or working on)There's also no way i'd be using some hooky DC/DC converter i found on ebay or wherever to power anything that has an critical RF system in it.E

author: theleakydiode
author_rank: Regular Contributor
timestamp: February 10, 2018, 01:44:48 pm
content: What about some of those buck modules you find on ebay? I know its not the local market but they might be your best option, a linear regulator will drop 12W at those load currents and in>out differentials. That's a lot of heat even with a good heatsink.Buck modules are cheap and will dissipate about 1-2w maximum at full load current. If you need a bit of filtering for the radio circuit then slap an LC filter on the output, say a 1-10uH and a low ESR capacitor maybe a few tens of uF.Alternatively go to an auto-parts store and they might have 24v to 12v converters that plug into the cigarette lighter socket, I'm sure they must exist as lots of trucking equipment is 24v whilst appliances used in the cab are more commonly 12v.

author: Zero999
author_rank: Super Contributor
timestamp: February 10, 2018, 02:15:45 pm
content: Mouser seem to have a better stock, than Digikey. Here are the search results:24V in, 12V out, >1A <5A.The cheapesthttps://www2.mouser.com/ProductDetail/CUI/VXO78012-1000?qs=sGAEpiMZZMsc0tfZmXiUnQ%252bwKZhbvwnuBKzimGXrb31aIcHwaSyVLA%3d%3d

author: John Heath
author_rank: Frequent Contributor
timestamp: February 10, 2018, 02:49:30 pm
content: I can second this. I know someone that fixes buses. 12 volts is tapped of the first battery direct. With this is a DC to DC converter from 24 volts to keep the charge state of the 2 batteries in balance. In short they use the 24 volt line to give the first 12 volt battery extra charge to compensate.I can not help but wonder why they want 12 volts at 1 amp? This sounds like the requirements for a 2 amp USB cell phone charger. Could it be that what they really need is a 2 amp USB to charge a cell phone not a 12 volt 1 amp cigarette lighter type plug?

author: ivan747
author_rank: Super Contributor
timestamp: February 10, 2018, 08:44:27 pm
content: Quote from: ez24 on February 10, 2018, 02:42:53 amThanks for that important observation!

author: ivan747
author_rank: Super Contributor
timestamp: February 10, 2018, 08:46:20 pm
content: Quote from: Tomorokoshi on February 10, 2018, 02:23:04 amI might add a series resistor. This morning I was characterizing the device. I couldn’t see it exceeding 250mA under heavy use which is good news for the regulator.Still, I haven’t actually tested it in the real scenario, so I have no idea what’s gonna happen in the real world.

author: ivan747
author_rank: Super Contributor
timestamp: February 10, 2018, 08:47:23 pm
content: Quote from: John Heath on February 10, 2018, 03:33:08 amI will let you know by Monday.

author: ivan747
author_rank: Super Contributor
timestamp: February 10, 2018, 08:48:34 pm
content: Quote from: SeanB on February 10, 2018, 05:26:57 amDo these product go by a commercial name?For example, a 12V to 5V DC-DC converter for automotive use is also called a phone charger...

author: ivan747
author_rank: Super Contributor
timestamp: February 10, 2018, 08:50:01 pm
content: By the way, I located a shop that sells 24V to 12V converters, 5A capacity. But I forgot to ask about stock and the guy wouldn’t pick up the phone again... that guy definitely wasn’t the owner of the store.Sent from my iPhone using Tapatalk

author: tautech
author_rank: Super Contributor
timestamp: February 10, 2018, 08:51:53 pm
content: Quote from: ivan747 on February 10, 2018, 08:50:01 pmThere's many flavors available:https://www.google.co.nz/search?q=automotive+voltage+converter&rlz=1C1CHBF_enNZ760NZ760&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwi0zujSnJzZAhUMfLwKHTqpDB8QsAQIUA&biw=1096&bih=579

author: ivan747
author_rank: Super Contributor
timestamp: February 10, 2018, 08:52:09 pm
content: Quote from: HighVoltage on February 10, 2018, 08:59:29 amInteresting, I didn’t know there was an electronics industry like that in Haiti. I guess it must exist because they must have needs like ours.I’ll shop around on Monday afternoon I think.

author: ez24
author_rank: Super Contributor
timestamp: February 10, 2018, 09:02:06 pm
content: I think this would make a good video.Lot of things going on.

author: Zero999
author_rank: Super Contributor
timestamp: February 10, 2018, 10:17:37 pm
content: Quote from: ivan747 on February 10, 2018, 08:50:01 pmWhat's wrong with Mouser and Digikey as I suggested? Don't they ship to the Dominican Republic?

author: mariush
author_rank: Super Contributor
timestamp: February 10, 2018, 10:34:28 pm
content: Look in stores for those phone chargers that plug in the cigarette lighter which can do 5v at 1A. Some of them are made with regular mc33063 or mc34063 and you could change a couple of resistors to get 12v out of them and maybe you'd have to change the input capacitor to handle 24v.No sure you'd get 1A out of them, and when i tried one the inductor used and the other components were picked so lousy that the thing was most efficient at around 9v input and from memory i think it did 5v at up to around something like 0.8a.orGet a bunch of 2-3A diodes and put them in series, each one drops around 0.5-0.8v @ 1A , so you have less than 1w dissipated per diode.Lower the 24v down to around 15v this way and then use a 7812 or LM1084 , LM1085 whatever you can find around.

author: ivan747
author_rank: Super Contributor
timestamp: February 10, 2018, 10:58:50 pm
content: Quote from: GeorgeOfTheJungle on February 10, 2018, 11:05:44 amIt was designed to run off a wall adapter.I have taken apart the device. The power circuit is behind a shielding can. I think I can pop the lid off that can. Let me check...

author: floobydust
author_rank: Super Contributor
timestamp: February 10, 2018, 11:01:23 pm
content: OP, use your balls and tell them a solution will take longer to come up with.I've seen a quick fix like this before- Ended up, the 24VDC vehicle transients killed the 12V supply, which then killed the load. Angry customers, angry management and blown up devices.Engineers are capable of miracles, but not when sales screws up, mistake in the project requirements etc. and a couple days before installation

author: ivan747
author_rank: Super Contributor
timestamp: February 10, 2018, 11:07:37 pm
content: Quote from: sokoloff on February 10, 2018, 12:48:49 pmFunny thing: there's at least one company that offers such service in DR. They have some dude in Miami who will take your package and carry it personally on the very next flight he can catch and hand deliver it to your door. I can't begin to image how much that service costs.

author: Niklas
author_rank: Frequent Contributor
timestamp: February 10, 2018, 11:40:35 pm
content: You can offload some of the dissipation in the 7812 by adding diodes in series with the input. 1N540x can dissipate the power loss without a heatsink. Indicated thermal resistance is approx 20'C/W with short leads compared to >50'C/W for the smaller 1N400x. Something to think about to secure operation on a hot summer day without good ventilation.Another option is to add a 7818 regulator as a preregulator to split the dissipation.

author: Zero999
author_rank: Super Contributor
timestamp: February 11, 2018, 12:06:39 am
content: Quote from: ivan747 on February 10, 2018, 10:58:50 pmIt appears I'm on your ignore list!What did I do? If you don't respond to this soon, I'll have to put you on my ignore list, so I no longer waste my time on you.

author: ivan747
author_rank: Super Contributor
timestamp: February 11, 2018, 02:13:21 am
content: Quote from: Hero999 on February 11, 2018, 12:06:39 amHey! Sorry for not replying! The converters look really nice and they're cheap.Unfortunately they said it's too risky to ship stuff, any delay and we're screwed.If the solution we end up going for is a temporary one (something like the 7812s), I think this converter is high on the list:https://www.mouser.com/ProductDetail/CUI/VXO78012-1000?qs=sGAEpiMZZMsc0tfZmXiUnQ%252bwKZhbvwnuBKzimGXrb31aIcHwaSyVLA==It would make a good 7812 drop-in replacement.

author: ivan747
author_rank: Super Contributor
timestamp: February 13, 2018, 02:09:40 am
content: Sitrep:Turns out half the vehicles had 24V to 12V step down converters for the stereo, so we took power from there. They were in a convenient location as well.The other half didn't have anything. I called around and found a shop that had the exact amount of step down converters I needed. Again, these were specifically designed for connecting 12V car stereos to 24V vehicles. I still wish I had some kind of extra filter, but that's the only thing I got.I took one apart and it just looks like there is one IC doing the job, the construction of the device is not that great... I didn't examine it very closely, as I didn't have much time. Hopefully its design filters out some of the brutality that you find in an automotive electrical system. As for thermals, I think it will be alright, we are using less than 20% of the current that it promises to deliver.If you are curious, it looks something like this:https://www.amazon.com/Pyle-PSWNV120-Power-Converter-Technology/dp/B003P1D82S/ref=sr_1_36?ie=UTF8&qid=1518487542&sr=8-36&keywords=24v+to+12v+step+down+converterThank you all for your help! It was nice to know I had from plan A to plan Z.

author: sokoloff
author_rank: Super Contributor
timestamp: February 13, 2018, 12:56:04 pm
content: Really appreciate when people come back and tell us how things went. Thanks for that!

author: rsjsouza
author_rank: Super Contributor
timestamp: February 13, 2018, 11:57:25 pm
content: Good that everything was solved nicely, Ivan! I was almost at the point of telling you to slap a 12V/6~12W in series with the load.I was following this thread with interest as I have seen myself in these hot waters quite a few times in the past when I lived in Brazil; sometimes the opportunity is too good to pass ($$$ or prestige), the schedule is insane and the local market is anything but crappy or "creative" (shoehorned) solutions. At least there, counting on a scheduled delivery on something coming from a foreign country is the same as playing roulette - one disgruntled or greedy customs agent and your package takes months to be freed.

author: ivan747
author_rank: Super Contributor
timestamp: February 16, 2018, 12:41:40 am
content: Just came back from finishing the installation. What a job! It took three of us two full days and a handful of extra DC-DC converters, as some pre-installations were not working. The extra ones were totally overkill, they were huge (15A). But that's what was available.Lessons learned:*Support from your people is the best support you have.*You can stick anything with 10lbs double sided tape as long as it's clean.*3M tape is the best tape.*You can't describe a connector over the telephone.Everybody seems happy!Thanks guys!