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schematic

simulate this circuit – Schematic created using CircuitLab

I am fairly new to electronics. I've been studying it for the last few months and have put together a few circuits. The problem I had was that none of my circuits worked even if I followed a design that i found. I don't know why, but the circuits worked with a 9volt battery rather than using a power adapter (ie, 9v 100ma adapter). As a hobbyist, I have been grabbing old devices around the home, pulled them apart, kept all the resistors,caps, etc and the now empty PCB's. I wanted to build (probably not the best idea for my first complete circuit design) a box that put out 36, 24, 16 and 12 volts. I had several KA431L IC's and a few 3010KM IC's. I had a transformer that tapped out at 14V, 10.3V and 3.6V and so i used the 3.6v to a ka431L to create a steady 2.5V reference voltage to run the other ka431l and the 3010km. The 2nd ka431l had the 14V across its kathode and was there to give me 36v and 24v (from a switch) and the 10.3 went to the 3010KM.

  1. I can't seem to get more than 6.6Vs from the 2nd ka431l and the 3010km didn't work at all in this circuit. I built each of these circuits before using a prototype board and in that setting they all worked. I just can't figure what I did here (I'll include a picture)
  2. Is this even an acceptable Voltage Regulator circuit? Will I be able to run my DC circuits from this? I wonder if it safe, efficient, could have been done a better way, etc.
  3. I couldn't work out which ground each IC was expecting. ie. i send 14V DC over the 2nd KA431L kathode but I am powering it from the 1st KA431L into the Vref. At the anode, should it be the ground from the 14VDC or from the 1st KA431L?

Legend: BR - Bridge SW - Switch JP - Jumper to a second board HV1 - connections to the 3010km. each pin corresponds. TP - Test Point. I have pins that i can attach my multimeter to at various places in the board SB - The second board. it's shown on the schematic below

All the "c" "r" and other circuit symbology shown on the schematic are only references to where exactly on the up-used PCB i am connecting to or from. These references can be ignored.

I've broken the board into 3 Ground sections which I refer to as PCB Ground. For each IC on the board, there is a corresponding ground area unconnected from other grounds.

enter image description here

RobMcN
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  • I don't know that the schematic is so terrible. Three bridge rectifiers, the capacitors needed to smooth out the voltage, then the manufacturers guidelines around each of the three main components: ka431L x 2, 1 3010KM. The rest of the 'wiring' in the schematic is just to fit this into a random PCB board. and then 2 dpdt switches to modify the two voltage divider circuits. It's around these two switches I think I'm having trouble. – RobMcN Jun 01 '20 at 21:52
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    @Starblazer When building anything that is complex, and especially when you are new to electronics, you need to break it down into "sections" and test each of them, separately, before combining them. Sit down, come up with a build-test strategy, and follow it, closely. If you need help in developing such strategies, give us a complete schematic you intend on building (or have built when it didn't work) using the editor available here and ask for advice about how to lay out a step-wise plan of attack. I think folks here could help produce something like what Heathkit would do, if small enough. – jonk Jun 01 '20 at 22:08
  • @jonk Thanks for that. I'll do that. Mainly I'm concerned that it won't be good enough to do what I need it to do. I did prototype each section and each section worked but with the addition of the two switches seems to have done something I didn't predict and I don't know why. – RobMcN Jun 02 '20 at 00:27
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    @Starblazer I'd recommend that you use the schematic editor that is available here. A;so read my discussion about [how to draw schematics](https://electronics.stackexchange.com/a/308882/38098) and carefully break up the schematic along its "natural boundaries." It will go a long way in helping others help you. I really did try to read your schematic, but what I found is that I'd need to sit down and completely re-draft it -- and that assumes I could read all of it, which I also already know I cannot do. So that leaves me out of even trying to help, for now. – jonk Jun 02 '20 at 02:29
  • @jonk Schematic drawn using the embedded editor. My questions are:1. Why am I getting only 6.6V at IC2 (the 2nd ka431L). 2. When working properly, what are the disadvantages of this circuit as a workbench tool to run my prototypes? 3. 3010KM seems to not be working (hard to tell since manufacture recommends the Vout attached to the Vin) – RobMcN Jun 02 '20 at 17:42
  • @Starblazer Do you actually have a wire shorting IC1 and a wire shorting R3? – jonk Jun 02 '20 at 17:46
  • @jonk The IC1 is a KA431L which has three pins: Kathode, Anode and Vref. If you want to limit the regulation to Vref (2.5 V) the datasheet shows this configuration of connecting the Vref t the Kathode. As for R3 - I think you're right. On this drawing I show R3 shorting after the switch. One side of the switch is supposed to go to Vref 2.5V, through the voltage divider's second resistor attached to the dpdt switch and the other end attaches to both Vout and returns to voltage divider. I'll edit the schematic accordingly. It is how I drew it on paper, I messed up on the editor. – RobMcN Jun 02 '20 at 18:02
  • You need to connect the negative sides of the three sections together - otherwise the 2.45 volt reference you make with IC1 is just a random floating voltage for the other supplies. It also looks like you are expecting the regulators to produce higher output voltages than their inputs - shunt and linear regulators can't do that! – Peter Bennett Jun 02 '20 at 18:06
  • If the switches are DPDT you should show them as such, not as four separate SPSTs. – Peter Bennett Jun 02 '20 at 18:08
  • @Starblazer I'd recommend just using the SCR symbol (unless someone has a better suggestion) for the KA431L, then. You absolutely have to have a three-wire symbol. You cannot expect us to guess how things are connected when you use a two-wire symbol for it. – jonk Jun 02 '20 at 18:11
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    The 3010KM is probably not working because the Enable input (pin 1) must be held above 2.0 volts to enable it. – Peter Bennett Jun 02 '20 at 18:17
  • @PeterBennett Thank you! Ok, i wondered about which ground to provide IC2. Is it possible to connect all three grounds together? Also, the KA431L has a max Vref of 7V . The provided formula is: Vk=Vref*(1+(r1/r2)). So 2.495*(1+(10k/745) = 35.336. The Resistor of 100 ohms sets the current at the kathode. – RobMcN Jun 02 '20 at 18:18
  • Actually, you haven't shown any grounds in your circuit. The negative sides of the three sections must be connected together. (Ground is often the most negative point in a circuit, but not always, so you should always mark the point you want to consider as ground/.zero volts.) – Peter Bennett Jun 02 '20 at 18:23
  • @PeterBennett You also brought up another question I had. Please excuse my learning mind. The IC1 [ka431l] puts out 2.45V - and I gather from the datasheet that it 'promises' that output. So, that 2.45V is branched to the 3010KM Venable and the IC2 Ka431l Vref. Am I mistaken? – RobMcN Jun 02 '20 at 18:25
  • @PeterBennett Alright, is the 'negative' coming from the bridge rectifiers, terminating in their corresponding capacitors? Would the most negative ground be the 14VDC ground? And it's just fine to attach all three 'negative' points? That would be awesome. Although I'm in learning mode, there's little pieces I haven't yet learned about, obviously. One of my biggest questions, still, though is will this circuit work for what I want: power to my different prototype circuits? Do I need filtering or anything like that? – RobMcN Jun 02 '20 at 18:29
  • You only have one wire from the IC1 section to the rest of the circuit, so there is no telling what voltage the 3010KM thinks is on its Enable pin. You MUST connect the negative sides of the three sections together so they all have a common reference. – Peter Bennett Jun 02 '20 at 18:30
  • If the negative terminal of C4 and the negative side of the associated bridge rectifier are not connected to the 3010 ground terminal, that rectifier is not supplying any power to the 3010. If that connection is made, you'll only have about 13 volts at the input to the 3010, so you can't get more than about 12.5 volts out of it - certainly not 24 V. – Peter Bennett Jun 02 '20 at 20:04
  • @PeterBennett The datasheet for the 3010KM gives Vout = (Vref/R2)*R1) therefore: Vref= 2.5V, R2=10k, R1=64k. My answer is: 17, but the max Vout is 16V. – RobMcN Jun 02 '20 at 20:26
  • @Starblazer: in the voltage adjust network, R1 should connect between Vout and Adj, and R2 between Adj and Gnd - you have no connection to Adj, and the two adjust resistors in parallel. If the negative side of C4 was connected to the 3010 Gnd, you would have 13 V at the 3010 Vin pin, so you can't get more than 12.5 volts out of the 3010, regardless of the voltage setting resistors. Due to missing ground connections, you will have no volts at Vin and Enable, so you should have no output from the 3010. Fix the missing ground connections, and correct the schematic to show the actual circuit. – Peter Bennett Jun 02 '20 at 21:13
  • Comments are not for extended discussion; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/108961/discussion-on-question-by-starblazer-help-with-dc-output-power-circuit). – Voltage Spike Jun 05 '20 at 21:11
  • @user287001, the site is to help OPs, not us. Please do not describe their work as 'crap'. – TonyM Jun 07 '20 at 08:59
  • I removed that comment. –  Jun 07 '20 at 09:17

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