I bought some LT-1073 DC to DC converter chips from Digi-key for about $4.00 apiece. \u00a0I’m going to try to make something small to power 9 volt radios and other devices. \u00a0It will use a 1.5 volt AA cell for the input \u00a0battery.<\/p>\n
The switching transistor is on the chip so the only parts that are needed are the inductor, a Schottky diode, a few capacitors and a two resistor V divider to set the output voltage. \u00a0The data sheet specifies 1 percent resistors but that kind of accuracy is not needed for a simple 9 volt power supply. \u00a0I calculated that a 1 Meg resistor and two 47k resistors in parallel should give about 9V.<\/p>\n
The inductor is shown as 120 Microhenrys. \u00a0I’m going to use either a toroid or a pot core to minimize interference as recommended in the data sheet. \u00a0I have plenty of 180 microhenry chokes so I’m going to try one of those. \u00a0The graph in the data sheet shows a minimum value which is 120 uH, but I don’t have that value, which is hard one to find. \u00a0I may have to wind my own on a toroid core, which is easy to do. \u00a0I have some small cores that should work okay.<\/p>\n
They talk about using low ESR capacitors or else a tantalum capacitor. \u00a0I’m going to use a regular 470uF electrolytic and another 0.1 uF capacitor across it, mainly because I found that they do a good job in my other DC to DC converters. \u00a0Maybe I should order these low ESR capacitors that they recommend, if I can find them for a reasonable price. \u00a0They’re OS-CON. \u00a0I checked the catalog and found that they’re over $1 apiece in quantities of 10 or more. \u00a0ouch.<\/p>\n
I spent a few hours drawing a layout of the circuit on strip board. \u00a0I then mounted the parts on a piece of real strip board. \u00a0I used the 9 Volt schematic that’s in the data sheet. \u00a0The only change I made is to use a 910 K 5% resistor and 22k 5% resistor. \u00a0The 1 percent resistors they show are not necessary. \u00a0I also added a 470 Microfarad capacitor across the 1.5v battery. \u00a0I only had to make 3 cuts to the strips. \u00a0I sound a toroid core with some 24 gauge insulated wire to get 120 microhenrys. \u00a0The DC resistance of the toroid winding was very low, below a tenth of an ohm.<\/p>\n
I added red and black wires to the input and output. \u00a0I double checked to make sure everything was wired correctly. \u00a0I hooked it up to the power and a voltmeter to the output. \u00a0It measured 9.27v for awhile. \u00a0then the voltage started dropping down to 9.2 volts. \u00a0When it got to that point it jumped back up to 9.2 7 Volts. \u00a0It continued to do this as long as there was no load. \u00a0I think the larger capacitor on the output causes this peculiarity. \u00a0If it had been smalVoltage voltage would probably not jump up and down so much.<\/p>\n
I used a 1k resistor for a load, to make it easy to figure out the load current – 9 volts cross the resistor gives 9 milliamps load current. \u00a0As shown in the data sheet it’s capable of putting out 9.27 milliamps at 9.27 volts when the input was 1.5 volts. \u00a0But when I set the input at 1.00 volts then the output dropped to 8.7 volts. \u00a0So it will need a fresh battery often. \u00a0The input current went up to 250 milliamps with the 1k load.<\/p>\n
I added a 9v battery snap-on connector to the output, and tomorrow I’m going to try to find a device that uses a 9 volt battery and only draws about 10 milliamps. \u00a0Most pocket radios draw 2 or 3 times that much so I don’t believe that this converter will be able to power a pocket radio. \u00a0The closest thing at hand is a digital multi-meter. \u00a0I would really like to power a regenerative receiver so I can find out how much RF interference this converter puts out.<\/p>\n
BTW, I’m not a fan oof Digikey, mainly because they’re not the cheapest distributor. \u00a0And yesterday I got a CD in the mail – at least that’s what I thought it was. \u00a0When I opened it up, POP! \u00a0This paper cube popped out. \u00a0It has a rubber band that pulls it into a cube from its flattened state in the CD folder. \u00a0I thought to myself, that was a really big waste. \u00a0Now they’ll probably send me a full size paper catalog in the mail. \u00a0It will probably cost several dollars to print and mail. \u00a0These are just another couple reasons why I don’t like Digikey.<\/p>\n
Note: I have been using my Android phone to enter the text in this and previous blogs. \u00a0Some text is answered – oops- entered by using the voice-to-text app. \u00a0I have to double check the text because this “feature” sometimes does very strange things, like translating certain words into complete and utter nonsense. \u00a0No matter how many times I check, the words might sneak through. \u00a0So forgive me 4 making some on the states – oops, did it again – odd mistakes occasionally. \u00a0These sometimes hilarious goofs were really its fault, not mine.<\/p>\n","protected":false},"excerpt":{"rendered":"
I bought some LT-1073 DC to DC converter chips from Digi-key for about $4.00 apiece. \u00a0I’m going to try to make something small to power 9 volt radios and other devices. \u00a0It will use a 1.5 volt AA cell for the input \u00a0battery. The switching transistor is on the chip so the only parts that <\/p>\n (Read More…)<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-9352","post","type-post","status-publish","format-standard","hentry","category-joule-thief-smps-dc-dc"],"_links":{"self":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/9352","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=9352"}],"version-history":[{"count":33,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/9352\/revisions"}],"predecessor-version":[{"id":9355,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/9352\/revisions\/9355"}],"wp:attachment":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=9352"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=9352"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=9352"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}