mb9 Posted May 1, 2005 Report Share Posted May 1, 2005 My grandson was born with an abnormally developed "X" gene. I believe he inherited the condition from his father who seems to enjoy anything a reasonable person would run from.In the interest of safety and my blood pressure, I'm looking for DC motor speed controller. Specifically, I need to limit the output of a 24 volt motor on a razor pocket bike. I was looking at this kit, http://electronickits.com/kit/complete/motor/ck1400.htm but I'm not sure it will work. Will this do the job ? Does it need a separate power supply? HELP!! Quote Link to comment Share on other sites More sharing options...
ante Posted May 1, 2005 Report Share Posted May 1, 2005 Hi mb9,Wellcome to this forum.The kit you found will run both itself and the motor from the same power source (battery) with no problem. I am not familiar with the razor pocket bike so I don’t know the maximum current draw for the motor though. The circuit can handle 5 A maximum on the pcb supplied with the kit.Best regards. Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted May 1, 2005 Report Share Posted May 1, 2005 Ante,The kit requires 5 to 16V while the razor bike's battery is 24V, I think this might fry it. You need a separate regulator to power the speed controler.This circuit will do the job and here's the LM7812C datasheet Quote Link to comment Share on other sites More sharing options...
ante Posted May 1, 2005 Report Share Posted May 1, 2005 Hi Alun,In this document : http://electronickits.com/kit/complete/motor/k166.pdf which I found on the link supplied you can find the specs for the k166 circuit. It will do the job fine as is. Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted May 1, 2005 Report Share Posted May 1, 2005 Sorry Ante, I was going on the information given here:http://electronickits.com/kit/complete/motor/ck1400.htmYou're right, I've also checked the capacitors andthey're rated to 63V, so this would be fine to run of 24V.It's an interesting circuit, I haven't seen a PWM controller with an H-bridge driver to reverse the motor before.The page on the site says it will work with motors up to 100V, but I assume you need a separate power supply for the motor. Quote Link to comment Share on other sites More sharing options...
ante Posted May 14, 2005 Report Share Posted May 14, 2005 Alun,From the schematic I can see no reason to have separate power for the motor, but I might be wrong. Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted May 14, 2005 Report Share Posted May 14, 2005 Then it must be a typo as it says it's suitable for motors up to 100V here: http://electronickits.com/kit/complete/motor/ck1400.htm Quote Link to comment Share on other sites More sharing options...
ante Posted May 14, 2005 Report Share Posted May 14, 2005 I agree if the motor voltage is higher than 32 Volts (as the spec says) the circuit must be separated. Its easily done by opening up the circuit at D3 and put in a regulator. Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted May 15, 2005 Report Share Posted May 15, 2005 It's not that simple Ante, Q3 and Q5 need the gate voltage to be near the source voltage to turn off properly, and as the sources are connected to +V running the comparators of a lower voltage will cause the transistors to remain on all the time. Quote Link to comment Share on other sites More sharing options...
audioguru Posted May 16, 2005 Report Share Posted May 16, 2005 Hi Alun,Good point! ;DDuh, since the Mosfets are common-source voltage amplifiers, don't they amplify the supply voltage? He, he. ;D ;D Quote Link to comment Share on other sites More sharing options...
Junaid Posted May 20, 2005 Report Share Posted May 20, 2005 u can build bridge by using UDN and ULN ICs for DC motor Controlling Quote Link to comment Share on other sites More sharing options...
ante Posted May 21, 2005 Report Share Posted May 21, 2005 Hi Alun,I know that, but it depends on how much the voltage has to be lowered. Anyway it’s a stupid point to discuss since mb9 was going to use it for 24Volts so I don’t know why I even mentioned it! Back to square one, I still say this circuit works! Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted May 21, 2005 Report Share Posted May 21, 2005 Hi Alun,I know that, but it depends on how much the voltage has to be lowered.You might be able to get away with a couple of volts, D3 and R15 already make the power supply to the op-amp circuit about 0.7V < than the motor. This may be fine but if the gate voltage on Q2 and Q5 is more than a couple of volts below their sources they will get turned on slightly 1V might be acceptable but 3V might cause a significant current to flow and if Q4 or Q6 is turned on ther would be a short circuit. Anyway it’s a stupid point to discuss since mb9 was going to use it for 24Volts so I don’t know why I even mentioned it! Back to square one, I still say this circuit works!I don't know Ante I think 24V might put a strain on the gates of the MOSFETs, their maximum gate to source voltage is only 20V.http://www.ozitronics.com/data/irfz44n.pdfhttp://www.irf.com/product-info/datasheets/data/irf4905.pdf Quote Link to comment Share on other sites More sharing options...
ante Posted May 21, 2005 Report Share Posted May 21, 2005 Referring to the specs:“The kit and motor use the same power supply. Since the maximum operating voltage of the LM324 is 32VDC then this is also the maximum voltage available to run the motor”! I understand this as; the circuit will work at 24VDC, but if I am wrong about this I have to blame it on my lousy English! Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted May 21, 2005 Report Share Posted May 21, 2005 Referring to the specs:“The kit and motor use the same power supply. Since the maximum operating voltage of the LM324 is 32VDC then this is also the maximum voltage available to run the motor”! I understand this as; the circuit will work at 24VDC, but if I am wrong about this I have to blame it on my lousy English! Ante, your English is perfect, I think this is an error in the kit.The problem is not with the LM324 which will be fine all the way up to 32VDC, the problem is that the maximum gate to source voltage the MOSFET can stand is only 20V. Often people oversee this a MOSFET might have a maximum VDSS of 55V but the gates on most MOSFETs is limited to 20V or less, and I can't see anything in this circuit to limit the gate voltage to the MOSFET.http://www.ozitronics.com/data/irfz44n.pdf Quote Link to comment Share on other sites More sharing options...
ante Posted May 22, 2005 Report Share Posted May 22, 2005 Hi Alun,Yes I can see what you mean. I am not used to check commercial circuits down to component level specs (maybe I should). But this will of curse put up a warning sign in big letters for this company! :o [move]Don’t buy anything here unless it’s checked in detail first! Contact Alun for consultation! ;D ;D ;D ;D[/move] Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted May 22, 2005 Report Share Posted May 22, 2005 Zener diodes connected between the gates an sources will solve this problem, I recommend 18V zeners.A small driver circuit for Q3 and Q5 would also allow you to power the motor from a higher supply voltage but to use 100V you'd need higher voltage MOSFETs.If you're interested I'll modify this circuit when I get round to it. Quote Link to comment Share on other sites More sharing options...
ante Posted May 24, 2005 Report Share Posted May 24, 2005 Thanks but I wouldn’t do it this way any way, but if mb9 isn’t a “one poster” he might like your help on this. But of curse he just needs the zeners since he like to use 24 Volts. Quote Link to comment Share on other sites More sharing options...
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