MP Posted July 23, 2006 Report Share Posted July 23, 2006 Hey gogo,Sorry for the late reply. I was on a business trip in Asia for the week and just got back this morning.Here are the eagle files for both schematic and board. Feel free to make any changes you need. This zip has a parts list for the LEDs used in the design if you would like to use them. Otherwise, you might have to make changes to the schematic for the one you want to use. Also, you might be able to use one of the edit commands to just use a different package in the board layout.MPicl7107-7106.zip Quote Link to comment Share on other sites More sharing options...
hungmao Posted August 8, 2006 Report Share Posted August 8, 2006 Hi,I'm a newbie here. I just want to share some experience in doing this project since many problems encountered are very similar to other big brothers.I have done this project with Smart Kit version and created the PCB with information in this webpage. Mine is configured in 20v DC range. In the very beginning, after I have finished, I found that the measured voltage cannot be locked with fluctuation of about 0.6v (my measured voltage should be regulated 4.5v, fluctuation range = 4.2v to 4.8v). I have measured the target voltage with another multimeter and confirmed that this voltage is stable. After the troubleshooting, I found that the following steps can help to mitigate the problems:(1) flux residues must be clear after soldering.(2) my voltmeter sourced by LT1085 regulated in +5v and attain -5v from ICL7660. But, my transformer's secondary output shared command ground with another power supply(9v-0-9v). The fluctation problem is mainly come from here. After separated the transformer, the fluctation solved in a great extent with only 0.05v (acceptable range for me).(3) proper grounding and shielding for the voltmeter circuit.Just my two cents. Hopefully these can help. Quote Link to comment Share on other sites More sharing options...
MP Posted August 10, 2006 Report Share Posted August 10, 2006 These are all good tips no matter what project you are working on. Thanks for sharing with everyone.MP Quote Link to comment Share on other sites More sharing options...
pier Posted August 23, 2006 Report Share Posted August 23, 2006 yes if ur taking the +ve voltage from the transformer o/p put a 1n4007 in reverse and the capacitor in reverse and then put a 7905 to get -ve voltag . Quote Link to comment Share on other sites More sharing options...
vicious5id Posted August 30, 2006 Report Share Posted August 30, 2006 Hey wassup people! Man tonnes of work has gone into this circuit, I'm very impressed with all these radical ideas about thermometers and ammeter adaptations! Who'd have thought an IC first manufactured in 1977 (7106, 7107 is the sister IC) would still be so very useful today!Anyway I just wanted to clear up a few things:a) http://www.electronics-lab.com/projects/test/007/index.htmlb) http://www.electronics-lab.com/projects/test/014/index.html^ Are those two circuits exactly the same, if not do they accomplish the exact same thing?I know that this project can be converted into an ammeter, I'd like to know if any of the above circuits (a & b) will measure current from 0 to 200 mA? Or better yet, 0 to 120 mA only. I have a circuit that supplies 0 to 120 mA to a 100 Ohm load and I want to know if this project can measure the current in the load to .1 decimal places perhaps.Is it a simple case of using a 10 Ohm resistor for R3 according to circuit b? Will that give me a 0 - 200 mA display if I hooked this up as an ammeter?Appreciate any replies.v5 out. Quote Link to comment Share on other sites More sharing options...
audioguru Posted August 30, 2006 Report Share Posted August 30, 2006 Hi Vicious,You want the current-measuring resistance to be as low as possible. You don't want to lose too much voltage across it nor ruin voltage regulation.The IC is capable of providing a full-scale voltage of only 200mV but the Smart Kit version has 2.0V. Then if you use the Smart Kit version with a 10 ohm current-measuring resistor for 200mA full-scale, the circuit you are measuring will have up to a 2.0V loss and its voltage regulation will be terrible. Quote Link to comment Share on other sites More sharing options...
vicious5id Posted August 31, 2006 Report Share Posted August 31, 2006 So you think that I should use circuit (a)?Which circuit will give me the smallest amount of loss?I understand that you need to measure the voltage across a small resistance to use a digital ammeter. Quote Link to comment Share on other sites More sharing options...
audioguru Posted August 31, 2006 Report Share Posted August 31, 2006 So you think that I should use circuit (a)?Which circuit will give me the smallest amount of loss?You should use the circuit in the datasheet. Circuit (a) is similar to it. It has a max of only a 200mV loss. Quote Link to comment Share on other sites More sharing options...
MP Posted August 31, 2006 Report Share Posted August 31, 2006 V5,This thread was actually started from schematic (b). It is also the most common one used, since the LEDs are more common.There is not a significant difference on these two projects other than the dual LEDs. They both get the same job done. Schematic (b) should be a little more stable since it has a smoothing capacitor across the input. Other members have reported that schematic (a) shows some instability in displaying the numbers. Too sensitive without the cap.Also, go back to reply # 26 in this discussion. This is where discussion of using this chip for an ammeter starts. You will most likely find some information there that will be helpful.I highly recommend that you read all of the replies in this thread. I compiled three different conversations into one thread so that all of the discussions were in the same area.MP Quote Link to comment Share on other sites More sharing options...
STEVE Posted September 7, 2006 Report Share Posted September 7, 2006 This may already have been answered on previous pages ... but don't have time to read all 19 at the minute!In the power supply which supplies the +/- 5 V (schematic attached) what are the two 1 K resistors for?Thanks Quote Link to comment Share on other sites More sharing options...
audioguru Posted September 7, 2006 Report Share Posted September 7, 2006 what are the two 1 K resistors for?To make a 0V reference voltage for the circuit. It is supposed to have a positive 5V supply and a negative 5V supply. Quote Link to comment Share on other sites More sharing options...
vkssingh Posted November 27, 2006 Report Share Posted November 27, 2006 I have gone through all the 19 pages on board but still some questions remained to be answered:I want to use this VM to measure car battery voltage, what should be the ground point in this case? This has been asked earlier also but no replies.If I use the car battery (12V) as input to 7805 and 7905 to genrate +5 V and -5V to power the IC will it work ? Will the Quote Link to comment Share on other sites More sharing options...
audioguru Posted November 27, 2006 Report Share Posted November 27, 2006 Hi Vk,A 7905 regulator isn't a generator. It takes a higher negative voltage and regulates its voltage down to -5V. It needs a negative voltage source as its input.There are a few ways of converting a positive voltage into a negative voltage. The datasheet for the ICL7107 IC in the project shows the circuit for one way. A 555 or an ICL7660 can also make a negative supply.A 7805 positive regulator needs a minimum input voltage of +7.5v. A 7905 negative regulator needs a minimum input voltage of -7.5V. Therefore their total minimum input voltage is 15V which is not available in a car anyway. Quote Link to comment Share on other sites More sharing options...
vkssingh Posted November 28, 2006 Report Share Posted November 28, 2006 Thanks for reply, I have decided to use IC555 to generate -5V as it is cheap and easily available, In such case should I take +5 V from output of 7805 to make -5V OR it is better to generate -12V with IC555 and then regualte it to -5 V using 7905?Will -ve terminal of battery be the ground point in the circuit? Quote Link to comment Share on other sites More sharing options...
audioguru Posted November 28, 2006 Report Share Posted November 28, 2006 It is best to make a +5V with a 7805 and make -12V from a 555 then regulate it with a 7905 to get -5V.The datasheet shows the ground of the meter connected to its negative input lead. The same ground as the negative terminal of the car battery. Quote Link to comment Share on other sites More sharing options...
MP Posted November 28, 2006 Report Share Posted November 28, 2006 I have gone through all the 19 pages on board but still some questions remained to be answered:I want to use this VM to measure car battery voltage, what should be the ground point in this case? This has been asked earlier also but no replies.If I use the car battery (12V) as input to 7805 and 7905 to genrate +5 V and -5V to power the IC will it work ? Will the Quote Link to comment Share on other sites More sharing options...
vkssingh Posted November 28, 2006 Report Share Posted November 28, 2006 Thanks for clarification, can you suggest what capacitor value to be used to supress the alternator noise?Since I shall be meauring battery voltage can I eliminate the -ve voltage and leave the IC7107 pin unconnected? I will put a diode in the supply line to avoid wrong polarity apllied to IC. Will it work?VK Quote Link to comment Share on other sites More sharing options...
audioguru Posted November 28, 2006 Report Share Posted November 28, 2006 Since I shall be meauring battery voltage can I eliminate the -ve voltage and leave the IC7107 pin unconnected? I will put a diode in the supply line to avoid wrong polarity apllied to IC. Will it work?Don't you have the datasheet for the ICL7107 that is used in this project?It says that the inputs don't work near ground (outside the input common-mode range) unless it has a negative supply, and a few other problems must be solved. Quote Link to comment Share on other sites More sharing options...
vkssingh Posted November 29, 2006 Report Share Posted November 29, 2006 One may be last question before I start construction: the capacitors in the circuit have to be ceramic or other types may also be used. Quote Link to comment Share on other sites More sharing options...
MP Posted November 29, 2006 Report Share Posted November 29, 2006 You will have to experiment a little on the capacitor size for the alternator noise. This is the same problem you might encounter with anything you build and add to your car. You might even need to use a choke and build an alternator noise filter if you have a lot of noise in your system. It will depend a lot on your car make, how old the alternator is, how worn out it is, etc. It is also possible that you will not even need to do anything at all. I would try no filtering at first and then add on to the design as needed.Ceramic capacitors? I would recommend that you use better capacitors.MP Quote Link to comment Share on other sites More sharing options...
vkssingh Posted November 30, 2006 Report Share Posted November 30, 2006 Would you pls suggest the capacitor and resistor types for the project?Thanks Quote Link to comment Share on other sites More sharing options...
MP Posted November 30, 2006 Report Share Posted November 30, 2006 I use 1% tolerance resistors for everything. R3 in this project must have such accuracy, but the others could be 5% if you have trouble getting 1% tolerance in your area. Ceramic caps are cheap, but they are not real good, either. If you use a higher grade material such as poly, mylar and tantalums, you will have better results. There is no problem using Electrolytic capacitors for the supply bypass lines. There might be some guidelines in the data sheet regarding this as well. This is not a big issue. If you use ceramic caps, the project will work. In fact, the Smart Kit probably uses the cheapest components off the shelf. This was only a suggestion to a better product.MP Quote Link to comment Share on other sites More sharing options...
SKIPPER Posted November 30, 2006 Report Share Posted November 30, 2006 Hi guys,Just finished to build this project for 0-20V range and it looks like I have a problem: instead of 12.00 V, for example, the display shows 00.12V, instead of 07.00 V it shows 00.07V and so on.What should I do to make it show the correct value with two decimals? Thanks. Quote Link to comment Share on other sites More sharing options...
MP Posted December 1, 2006 Report Share Posted December 1, 2006 What did you use for R3? Also which pin 5 did you jumper on the display?MP Quote Link to comment Share on other sites More sharing options...
SKIPPER Posted December 1, 2006 Report Share Posted December 1, 2006 Hi MP,Have used R3 = 1.2 Kohm 1% tollerance as described in the project page for 0 - 20 V range.I have connected the pin #5 of the 2nd display (from left to right) to the R6 resistor.Thanks for support and also for sharing this very useful project. Quote Link to comment Share on other sites More sharing options...
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