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Preamplifier For A Yamaha Electric Piano I own a Yamaha piano (as distinct from a keyboard). The piano doesn’t have enough output amplitude from ‘Aux Out’ to drive an amplifier, hence the need for a stereo preamp such as that described in April 1994. In the kit, three alternatives are offered namely: magnetic cartridge, tape/cassette deck and microphone. I’m assuming that the RIAA curve would not be relevant and neither would the microphone option. I am intending to wire in the tape or cassette option. Am I correct or can you suggest another option for low output pianos? (D. V., via email). resistor may be required to limit the maximum current in each coil. The Sensym ASDX015A24R is hard to get. We recommend that you use an automotive MAP sensor. You can obtain new MAP sensors from: www.cyberspaceautoparts.com.au/contents/ en-uk/d3721_Holden_Map_Sensors. html or from similar suppliers. A secondhand MAP sensor can be obtained from a wreckers yard. We used a standard V6 MAP sensor in our prototype. 500W speed control for a 240V DC brush motor I have a 230-240V DC 500W brush motor that has been removed from a treadmill and I need to be able to vary its speed. Would the new 230VAC Speed Controller For Universal Motors (SILICON CHIP, February & March 2014) work on this motor? (A. C., via email). • Yes, this motor speed controller works with 240V DC motors. However, we suspect that your treadmill motor may be a standard universal AC motor. This is a series-wound brush/commutator motor which will run equally well on AC or DC. Extra slaves for Micromite Can you have more than one slave connected to a Master Micromite via the I2C connection, as in Fig.8 on page 73 of the June 2014 issue. If so, how? Also, have you considered modifying the 30A DC Relay project (No104  Silicon Chip • None of the suggested options in the article would be suitable. The RIAA and Tape options have frequency tailoring and high gain while the microphone option has too much gain. Your Auxiliary output should have 100mV or more and typically 250mV, so a gain of four would probably be the maximum you need. We suggest the same arrangement as the microphone option with R4 at 390Ω and R1 a wire link. The R2 value would only need to be 1kΩ for a gain of 3.56. If you need more gain, use a 2.2kΩ or 4.7kΩ resistor; for less gain, use an 820Ω resistor. Capacitor C2 can be 1nF. vember 2006) to have four or eight DPDT relays on one circuit board? The outputs could use header pins and/or screw terminals. A relay rating of 1A would be OK. I think this would be a useful to connect to a Micromite. (J. S., via email). • Yes, you can attach multiple slaves to the one master. The only limitation is the number of I2C addresses that are available (112 devices). We do not have plans to modify the November 2006 project but yours is a good idea for the future. The board could also have inputs as well as relay outputs and could be controlled over I2C. We will have a look at it to see if it’s feasible. Ultrasonic cleaner may be wired incorrectly I have purchased and assembled your Ultrasonic Cleaner (SILICON CHIP, August 2010) and have a few issues you might be able to help me with. After assembly, I did the first electrical check as per your instructions, removing fuse F1 and IC1 from circuit. The regulator voltage was within parameters of 4.85V and 5.15V DC. The power light comes on but the unit won’t activate when set to timer or start and the run LED won’t light. I have included some photos to assist. Your thoughts on solving this problem would be appreciated. (B. F., via email). • From the photos you supplied it seems that only two wires are connected on the PCB for the timer po- Advertising Index Altronics.................................. 72-75 Aust. Exhibitions & Events............ 47 Consulting & Eng. 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Check also that all the IC pins are correctly inserted into the IC socket and not bent under SC the socket. siliconchip.com.au